Licenses Acquired - Additional Information (Detail)

v3.8.0.1

Licenses Acquired - Additional Information (Detail) - USD ($)					1 Months Ended																								9 Months Ended	12 Months Ended
		Jul. 03, 2017	Jul. 03, 2017	May 11, 2015	Jan. 31, 2018	Nov. 30, 2017	Nov. 30, 2017	Oct. 31, 2017	Jun. 26, 2017	May 31, 2017	Apr. 25, 2017	Mar. 31, 2017	Mar. 17, 2017	Feb. 17, 2017	Jan. 31, 2017	Oct. 31, 2016	Sep. 30, 2016	May 31, 2016	Feb. 23, 2016	Dec. 31, 2015	Oct. 31, 2015	Sep. 30, 2015	Sep. 18, 2015	Jul. 16, 2015	Jun. 17, 2015	Apr. 28, 2015	Mar. 31, 2015	Feb. 28, 2015	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 01, 2017	Jun. 01, 2017	Jul. 31, 2016	Mar. 17, 2014
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payments to Acquire Intangible Assets																														$ 0	$ 350,000	$ 1,250,000
Research And Development In Process																														4,164,000	5,532,000	11,408,000
Payments for Fees						$ 2,700,000	$ 100,000																						$ 1,265,000
Stock Issued During Period, Shares, Issued for Services																			10,000
Research And Development Expense																														52,486,000	35,134,000	29,810,000
Payments To Acquire In Process Research And Development																														3,365,000	3,785,000	10,448,000
Share Price																																	$ 3.83	$ 2.24
Proceeds from Issuance of Common Stock									$ 34,200,000
Share-based Compensation																														$ 14,005,000	12,128,000	14,291,000
Fair Value Assumptions, Expected Volatility Rate																														70.00%
Stock Issued During Period, Value, New Issues																															53,000,000
Stock Issued During Period, Shares, New Issues								43,292															10,000
Equity Method Investment, Ownership Percentage																																				35.00%
Development Milestone [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue Recognition Milestone Method Payments Due																								$ 22,000,000				$ 10,700,000
Sale Millstone [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue Recognition Milestone Method Payments Due																								7,000,000				26,200,000
NeuPharma [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research And Development In Process																											$ 1,000,000			$ 600,000	1,000,000	0
NeuPharma [Member] | Development Milestone [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue Recognition Milestone Method Payments Due																											40,000,000
NeuPharma [Member] | Sale Millstone [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue Recognition Milestone Method Payments Due																											40,000,000
NeuPharma [Member] | Regulatory Approvals To Commercialize Products [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue Recognition Milestone Method Payments Due																											$ 22,500,000
City Of Hope [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Marketability Percentage Of Invested Capital																											44.80%
Payments for Fees												$ 100,000
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage																											30.00%
Share Price																											$ 0.147
Stock Issued During Period, Value, Other																											$ 100,000					100,000
Revenue Recognition Milestone Method Payments Due												100,000
City Of Hope [Member] | Development Milestone [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue Recognition Milestone Method Payments Due																										$ 1,500,000
City Of Hope [Member] | Sale Millstone [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue Recognition Milestone Method Payments Due																										13,000,000
National Institutes of Health [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payment of Upfront Milestone Fees																								700,000
New Zealand Pharmaceuticals Ltd [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Reimbursement Revenue																								600,000
UCLA License [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue Recognition Milestone Method Payments Due													$ 14,300,000
Tamid [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Share Price																														$ 0.015
Fair Value Assumptions, Expected Volatility Rate																														75.00%
Fair Value Inputs, Discount for Lack of Marketability																														40.50%
Equity Method Investment, Ownership Percentage																														10.00%
Proceeds from License Fees Received																														$ 15,000
Dana-Farber [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Shares Issued, Price Per Share				$ 0.065
Stock Issued During Period, Shares, Issued for Services				500,000																		136,830
Stock Issued During Period, Value, Issued for Services				$ 32,500																		$ 600,000
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners																														5.00%
Proceeds from Issuance of Common Stock																														$ 10,000,000
Dana-Farber [Member] | First Commercial Sale Milestone [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue Recognition Milestone Method Payments Due																						21,500,000
Dana-Farber [Member] | Additional Sales Milestone [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue Recognition Milestone Method Payments Due																						$ 60,000,000
Mustang Bio, Inc [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research And Development Expense																														600,000
Payment of Upfront Fees														$ 9,300,000,000
Revenue Recognition Milestone Method Payments Due														100,000
Royalty Guarantees, Commitments, Amount																											$ 1,000,000
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners																											10.00%
Minimum Annual Royalty Payable																											$ 1,000,000
Mustang Bio, Inc [Member] | Development Milestone [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue Recognition Milestone Method Payments Due																											14,500,000
Mustang Bio, Inc [Member] | Financial Milestone [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue Recognition Milestone Method Payments Due																											2,000,000
Escala Therapeutics, Inc [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payment of Upfront Fees																								$ 1,300,000								1,300,000
Gene Medicine, Inc [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue Recognition Milestone Method Payments Due																														19,300,000
Royalty Guarantees, Commitments, Amount																																	$ 100,000		$ 300,000
Effcon Laboratories, Inc [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payment of Upfront Fees																	$ 200,000
Revenue Recognition Milestone Method Payments Due																	5,300,000
Royalty Guarantees, Commitments, Amount																	$ 1,600,000
Teva Pharmaceutical Industries Ltd [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payments for Fees																				$ 500,000
Teva Pharmaceutical Industries Ltd [Member] | Regulatory Approvals To Commercialize Products [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue Recognition Milestone Method Payments Due																				206,500,000
Teva Pharmaceutical Industries Ltd [Member] | Clinical Development and Regulatory Milestone [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue Recognition Milestone Method Payments Due																				$ 220,000,000
Jubilant Biosys Ltd [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research And Development In Process																														2,000,000
Revenue Recognition Milestone Method Payments Due																														$ 87,200,000
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners																														50.00%
Payment Of Upfront Licensing Fee																		$ 2,000,000
Royalty Revenue																														$ 1,000,000	1,500,000	0
Jubilant Biosys Ltd [Member] | Sale Millstone [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Milestone Method Revenue Additional Payments Eligible To Receive																		89,000,000
Jubilant Biosys Ltd [Member] | Regulatory Approvals To Commercialize Products [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue Recognition Milestone Method Payments Due																		59,500,000
Jubilant Biosys Ltd [Member] | Completion Of Three Clinical Development Milestones For Two Licensed Products [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue Recognition Milestone Method Payments Due																														25,500,000
Jubilant Biosys Ltd [Member] | Five Regulatory Approvals And First Commercial Sales [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue Recognition Milestone Method Payments Due																														61,700,000
Jubilant Biosys Ltd [Member] | Three Sales Milestones Based On Aggregate Net Sales [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue Recognition Milestone Method Payments Due																														89,000,000
Jubilant Biosys Ltd [Member] | Clinical Development and Regulatory Milestone [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue Recognition Milestone Method Payments Due																		$ 89,000,000
Jubilant Biosys Ltd [Member] | TG Therapeutics, Inc [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payment of Upfront Fees																														1,000,000
Columbia University [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Stock Issued During Period, Shares, Purchase of Assets															1,050,000
Shares Issued, Price Per Share															$ 0.028
Stock Issued During Period, Value, Purchase of Assets															$ 29,000
Payment of Upfront Fees															200,000
Revenue Recognition Milestone Method Payments Due															$ 5,500,000
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners															10.00%
Fair Value Assumptions, Expected Volatility Rate															70.00%
Fair Value Assumptions, Expected Term															5 years
Fair Value Assumptions, Risk Free Interest Rate															1.93%
Fair Value Inputs, Discount for Lack of Marketability															49.50%
National Institute of Child Health and Human Development [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payment of Upfront Fees												100,000
Collaborative Agreements with TGTX [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payments for Fees																														500,000
Collaborative Agreements with TGTX [Member] | NeuPharma [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payments for Fees																														84,000	42,000	600,000
Agreement With City Of Hope [Member] | Mustang Bio, Inc [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payment Of Upfront Licensing Fee																											2,000,000
Triplex [Member] | City Of Hope [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Minimum Annual Royalty Payable																										750,000
Pentameter [Member] | City Of Hope [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Minimum Annual Royalty Payable																										750,000
Pentameter [Member] | City Of Hope [Member] | Development Milestone [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue Recognition Milestone Method Payments Due																										5,500,000
Pentameter [Member] | City Of Hope [Member] | Sale Millstone [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue Recognition Milestone Method Payments Due																										26,000,000
Coronado SO Co, Inc [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research And Development In Process																														0	$ 0	$ 1,607,000
Shares Issued, Price Per Share								$ 4.6197
Payments for Fees																												$ 900,000
Stock Issued During Period, Shares, Other																												150,000
Research And Development Expense																					$ 500,000									$ 300,000
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners																				13.00%										13.00%	13.00%	13.00%
Payment For Research And Development Licenses								$ 50,000
Stock Issued During Period, Value, New Issues								$ 200,000
Proceed from sale of milestone payment																														$ 1,800,000
Checkpoint Therapeutics, Inc [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research And Development In Process																														400,000	$ 3,160,000	$ 3,159,000
Stock Issued During Period, Value, Purchase of Assets																														$ 22,000,000
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	[1]																			62.30%										62.00%	62.90%	62.30%
Checkpoint Therapeutics, Inc [Member] | First Commercial Sale Milestone [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue Recognition Milestone Method Payments Due																														$ 21,500,000
Checkpoint Therapeutics, Inc [Member] | Additional Sales Milestone [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue Recognition Milestone Method Payments Due																														60,000,000
Checkpoint Therapeutics, Inc [Member] | Clinical Development Milestone [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue Recognition Milestone Method Payments Due																														7,000,000
Checkpoint Therapeutics, Inc [Member] | Commercial Sales In Specified Territories [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue Recognition Milestone Method Payments Due																														14,500,000
Checkpoint Therapeutics, Inc [Member] | NeuPharma [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research And Development In Process																															$ 1,000,000
Checkpoint Therapeutics, Inc [Member] | Dana-Farber [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Stock Issued During Period, Value, Purchase of Assets																														4,200,000	5,500,000	$ 11,400,000
Helocyte [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research And Development In Process																										200,000				$ 0	$ 53,000	200,000
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners																														20.00%	20.50%
Helocyte [Member] | Triplex [Member] | Development Milestone [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue Recognition Milestone Method Payments Due																										9,000,000
Helocyte [Member] | Triplex [Member] | Sale Millstone [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue Recognition Milestone Method Payments Due																										26,000,000
Licensing Agreements [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payments to Acquire Intangible Assets																										$ 45,000	$ 150,000
Licensing Agreements [Member] | City Of Hope [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Marketability Percentage Of Invested Capital																		44.50%
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage																		30.00%
Share Price																		$ 0.097
Stock Issued During Period, Value, Other																		$ 48,500
Licensing Agreements [Member] | City Of Hope [Member] | Common Class A [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Noncash or Part Noncash Acquisition, Noncash Financial or Equity Instrument Consideration, Shares Issued																		500,000
Licensing Agreements [Member] | Dana-Farber [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payments for Fees																																$ 1,000,000
Licensing Agreements [Member] | Mustang Bio, Inc [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Stock Issued During Period, Shares, Issued for Services																															293,588
Stock Issued During Period, Value, Issued for Services																															$ 1,700,000
Share Price																															$ 5.73
Proceeds from Third Party Investors																															$ 10,000,000
Licensing Agreements [Member] | Cellvation Inc [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Marketability Percentage Of Invested Capital																40.20%
Stock Issued During Period, Shares, Issued for Services																500,000
Share-based Compensation Arrangement by Share-based Payment Award, Purchase Price of Common Stock, Percent																30.00%
Share Price																$ 0.024
Stock Issued During Period, Value, Other																$ 12,000
Payment of Upfront Fees																$ 300,000
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners																5.00%
Licensing Agreements [Member] | Cellvation Inc [Member] | Development Milestone [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue Recognition Milestone Method Payments Due																$ 6,200,000
Licensing Agreements [Member] | Cellvation Inc [Member] | Sale Millstone [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue Recognition Milestone Method Payments Due																6,000,000
Licensing Agreements [Member] | Cellvation Inc [Member] | Minimum [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Additional Minimum Annual Royalty Payable																50,000
Licensing Agreements [Member] | Cellvation Inc [Member] | Maximum [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Additional Minimum Annual Royalty Payable																200,000
Licensing Agreements [Member] | Cellvation Inc [Member] | Research and Development - Licenses Acquired [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Share-based Compensation																															$ 12,000
Licensing Agreements [Member] | IV Tramadol [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payments to Acquire Intangible Assets																									$ 1,000,000
Payments for Fees																												$ 2,000,000
Licensing Agreements [Member] | Coronado SO Co, Inc [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Marketability Percentage Of Invested Capital																														44.80%
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage																														30.00%
Share Price																														$ 1.19
Licensing Agreements [Member] | Helocyte [Member] | Common Class A [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Noncash or Part Noncash Acquisition, Noncash Financial or Equity Instrument Consideration, Shares Issued																		8,333
Avenue Therapeutics, Inc. [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Shares Issued, Price Per Share									$ 6.00
Debt Instrument, Fee Amount														$ 3,000,000
Secondary License [Member] | Cellvation Inc [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payment of Upfront Fees																50,000
Revenue Recognition Milestone Method Payments Due																300,000
Second TBI License [Member] | Cellvation Inc [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Minimum Annual Royalty Payable																$ 100,000
AR CD123 License [Member] | City Of Hope [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue Recognition Milestone Method Payments Due																														$ 14,500,000
AR IL-13 License [Member] | City Of Hope [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research And Development In Process																														500,000
Revenue Recognition Milestone Method Payments Due																														14,500,000
HER2 Technology License [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payment of Upfront Fees												600,000
Revenue Recognition Milestone Method Payments Due												14,900,000
Annual Maintenance Fee Payable												$ 50,000
CS1 Technology License [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payment of Upfront Fees			$ 600,000
Revenue Recognition Milestone Method Payments Due										$ 14,900,000
Annual Maintenance Fee Payable										50,000
PSCA Technology License [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payment of Upfront Fees			300,000
Revenue Recognition Milestone Method Payments Due										14,900,000
Annual Maintenance Fee Payable										$ 50,000
University of California [Member] | UCLA License [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payment of Upfront Fees											$ 200,000
Fred Hutchinson Cancer Research Center License [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payment of Upfront Fees			300,000
Revenue Recognition Milestone Method Payments Due		$ 39,100,000
Annual Maintenance Fee Payable			$ 50,000
Harvard College License [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue Recognition Milestone Method Payments Due																														2,700,000
Revenue Recognition, Sales and Marketing Milestone Method Payments Due																														$ 14,000,000
Harvard College License [Member] | Subsequent Event [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payment of Upfront Fees					$ 200,000
MPS1 license [Member] | Subsequent Event [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payment of Upfront Fees					85,000
Revenue Recognition, Sales and Marketing Milestone Method Payments Due					7,500,000
Revenue Recognition, Development Milestone Method Payments Due					$ 5,500,000
Revenue Recognition, Milestone Method, Extension Description					Extension for such milestones is $10,000 per milestone for the first year and $20,000 per milestone thereafter.
Nanadysferlin License [Member] | Subsequent Event [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payment of Upfront Fees					$ 85,000
Revenue Recognition, Sales and Marketing Milestone Method Payments Due					33,000,000
Revenue Recognition, Development Milestone Method Payments Due					$ 5,400,000
Revenue Recognition, Milestone Method, Extension Description					Extension for such milestones is $10,000 per milestone for the first year and $20,000 per milestone thereafter.
HLA-G License [Member] | Subsequent Event [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payment of Upfront Fees					$ 85,000
Revenue Recognition, Sales and Marketing Milestone Method Payments Due					42,000,000
Revenue Recognition, Development Milestone Method Payments Due					$ 5,400,000
Revenue Recognition, Milestone Method, Extension Description					Extension for such milestones is $10,000 per milestone for the first year and $20,000 per milestone thereafter.
[1] Checkpoint is consolidated with Fortress’ operations because Fortress maintains voting control through its ownership of Checkpoint’s Class A Common Shares which provide super-majority voting rights.