Fortress Biotech, Inc. Annual report pursuant to Section 13 and 15(d)

Licenses Acquired (Narrative) (Details)

Licenses Acquired (Narrative) (Details)							1 Months Ended									12 Months Ended		24 Months Ended
Licenses Acquired (Narrative) (Details)	Dec. 17, 2020 USD ($) Milestone	Dec. 17, 2019 USD ($) Milestone agreement shares	Oct. 15, 2015 USD ($)	Sep. 30, 2015 USD ($) shares	May 11, 2015 USD ($) $ / shares shares	Mar. 31, 2015 USD ($) Milestone	Dec. 31, 2019 USD ($) $ / shares installment	Jun. 30, 2019 USD ($)	Mar. 31, 2017 USD ($)	Oct. 31, 2016 USD ($) Milestone shares	May 31, 2016 USD ($)	Dec. 31, 2015 Milestone	Apr. 30, 2015 USD ($) Milestone	Mar. 31, 2015 USD ($)	Feb. 28, 2015 USD ($)	Dec. 31, 2020 USD ($) Milestone	Dec. 31, 2019 USD ($) $ / shares	Dec. 31, 2020 USD ($)
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research and development - licenses acquired																$ 2,834,000	$ 6,090,000
Research and Development Expense																64,109,000	81,326,000
Product revenue, net																44,531,000	34,921,000
Maintenance fees paid																50,000	25,000
Licensing Agreements [Member] \| Adimab Llc Collaboration Agreement [Member] \| Achievement of Each Milestones [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payments of milestones			$ 7,100,000
Licensing Agreements [Member] \| Adimab Llc Collaboration Agreement [Member] \| Upon Various Filings for Regulatory Approvals [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payments of milestones			$ 4,800,000
Aevitas [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research and development - licenses acquired																62,000	0
Aevitas [Member] \| Licensing Agreements [Member] \| University of Massachusetts [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research and development - licenses acquired																100,000
Number of net sales milestones \| Milestone	4
Aevitas [Member] \| Licensing Agreements [Member] \| University of Massachusetts [Member] \| Achievement of Each Milestones [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payments of milestones	$ 1,000,000.0
Aevitas [Member] \| Licensing Agreements [Member] \| University of Massachusetts [Member] \| Achievement of Certain Sales Milestones [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payments of milestones	$ 4,000,000.0
Avenue [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research and development - licenses acquired																0	1,000,000
Avenue [Member] \| Licensing Agreements [Member] \| IV Tramadol [Member] \| Revogenex Ireland Ltd [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Upfront fees payment															$ 3,000,000.0
Research and development - licenses acquired																0	1,000,000.0
Payments of milestones																3,000,000.0
Baergic [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research and development - licenses acquired																11,000	3,290,000
Baergic [Member] \| Licensing Agreements [Member] \| AstraZeneca [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research and development - licenses acquired																9,000	0
Number of license agreement \| agreement		2
Baergic [Member] \| Licensing Agreements [Member] \| Cincinnati Children's Hospital Medical Center [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Upfront fees payment		$ 200,000
Research and development - licenses acquired																2,000	0
Number of net sales milestones \| Milestone		4
Number of development milestones \| Milestone		2
Payments of milestones		$ 21,000,000.0
Common shares issued (in shares) \| shares		624,922
Reimbursement of past patent expenses		$ 30,000
Payment of upfront licensing fee		$ 6,500,000
Stock Issued During Period, Shares, New Issues \| shares		624,922
Percentage of common shares issued (in percent)		5.00%
Amount of net of debt utilized																	$ 100,000
Baergic [Member] \| Licensing Agreements [Member] \| Cincinnati Children's Hospital Medical Center [Member] \| Discount for Lack of Marketability [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Common Shares, measurement input							0.446										0.446
Baergic [Member] \| Licensing Agreements [Member] \| Cincinnati Children's Hospital Medical Center [Member] \| Measurement Input Weighted Average Cost of Capital [ Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Common Shares, measurement input							0.205										0.205
Baergic [Member] \| Licensing Agreements [Member] \| Cincinnati Children's Hospital Medical Center [Member] \| Share Price [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Common Shares, measurement input \| $ / shares							0.029										0.029
Baergic [Member] \| Licensing Agreements [Member] \| Maximum [Member] \| AstraZeneca [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Issuance of anti-dilution protection of shares		$ 15,000,000.0
Baergic [Member] \| Licensing Agreements [Member] \| AZ License [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Amount of net of debt utilized																	$ 100,000
Baergic [Member] \| Licensing Agreements [Member] \| AZ License [Member] \| Share Price [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Common Shares, measurement input \| $ / shares							0.029										0.029
Baergic [Member] \| Licensing Agreements [Member] \| AZ License [Member] \| AstraZeneca [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Upfront fees payment		$ 3,000,000.0
Number of net sales milestones \| Milestone		3
Common shares issued (in shares) \| shares		2,492,192
Stock Issued During Period, Shares, New Issues \| shares		2,492,192
Percentage of common shares issued (in percent)		19.95%
Baergic [Member] \| Licensing Agreements [Member] \| AZ License [Member] \| AstraZeneca [Member] \| Achievement of Each Milestones [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payments of milestones		$ 75,000,000
Baergic [Member] \| Licensing Agreements [Member] \| AZ License [Member] \| AstraZeneca [Member] \| Achievement of Certain Sales Milestones [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payments of milestones		130,000,000
Baergic [Member] \| Licensing Agreements [Member] \| AZ License [Member] \| AstraZeneca [Member] \| Discount for Lack of Marketability [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Common Shares, measurement input							0.446										0.446
Baergic [Member] \| Licensing Agreements [Member] \| AZ License [Member] \| AstraZeneca [Member] \| Measurement Input Weighted Average Cost of Capital [ Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Common Shares, measurement input							0.205										0.205
Baergic [Member] \| Licensing Agreements [Member] \| AZ License [Member] \| Maximum [Member] \| AstraZeneca [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Issuance of anti-dilution protection of shares		$ 75,000,000
Cellvation [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research and development - licenses acquired																1,000	$ 0
Cellvation [Member] \| Licensing Agreements [Member] \| Initial TBI License [Member] \| University of Texas [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Upfront fees payment										$ 300,000
Common shares issued (in shares) \| shares										500,000
Stock Issued During Period, Shares, New Issues \| shares										500,000
Percentage of common shares issued (in percent)										5.00%
Cellvation [Member] \| Licensing Agreements [Member] \| Initial TBI License [Member] \| University of Texas [Member] \| Development of Adult Indications [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Number of development milestones \| Milestone										9
Payments of milestones										$ 6,200,000
Cellvation [Member] \| Licensing Agreements [Member] \| Initial TBI License [Member] \| University of Texas [Member] \| Development of Pediatric Indications [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Number of development milestones \| Milestone										8
Payments of milestones										$ 6,000,000.0
Cellvation [Member] \| Licensing Agreements [Member] \| Initial TBI License [Member] \| Minimum [Member] \| University of Texas [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Additional Minimum Annual Royalty Payable										50,000
Cellvation [Member] \| Licensing Agreements [Member] \| Initial TBI License [Member] \| Maximum [Member] \| University of Texas [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Additional Minimum Annual Royalty Payable										200,000
Cellvation [Member] \| Licensing Agreements [Member] \| Second TBI License [Member] \| University of Texas [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Upfront fees payment										50,000
Research and development - licenses acquired																$ 1,000	0
Payments of milestones										300,000
Common shares issued, value																	500,000
Minimum Annual Royalty Payable										$ 100,000
Checkpoint [Member] \| Licensing Agreements [Member] \| Dana Farber Cancer Institute [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Upfront fees payment					$ 1,000,000.0
Common shares issued, value				$ 600,000	$ 32,500
Common shares issued (in shares) \| shares				136,830	500,000
Shares issued, price per share \| $ / shares					$ 0.065
Issuance of anti-dilution protection of shares					$ 10,000,000.0
Stock Issued During Period, Shares, New Issues \| shares				136,830	500,000
Annual Maintenance Fee Payable				$ 50,000
Checkpoint [Member] \| Licensing Agreements [Member] \| Dana Farber Cancer Institute [Member] \| Checkpoint [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners					5.00%
Checkpoint [Member] \| Licensing Agreements [Member] \| Dana Farber Cancer Institute [Member] \| Achievement of Each Milestones [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Issuance of anti-dilution protection of shares				21,500,000
Checkpoint [Member] \| Licensing Agreements [Member] \| Dana Farber Cancer Institute [Member] \| Achievement of Certain Sales Milestones [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payments of milestones				$ 60,000,000.0
Checkpoint [Member] \| Licensing Agreements [Member] \| NeuPharma, Inc. [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payment of upfront licensing fee														$ 1,000,000.0
Checkpoint [Member] \| Licensing Agreements [Member] \| NeuPharma, Inc. [Member] \| Achievement of Certain Sales Milestones [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payments of milestones														40,000,000
Checkpoint [Member] \| Licensing Agreements [Member] \| NeuPharma, Inc. [Member] \| Completion of Clinical Development Milestones [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payments of milestones														40,000,000.0
Checkpoint [Member] \| Licensing Agreements [Member] \| NeuPharma, Inc. [Member] \| Regulatory Approvals to Commercialize the Products [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payments of milestones														$ 22,500,000
Checkpoint [Member] \| Licensing Agreements [Member] \| Jubilant Biosys Ltd [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Upfront fees payment											$ 2,000,000.0
Checkpoint [Member] \| Licensing Agreements [Member] \| Jubilant Biosys Ltd [Member] \| Achievement of Certain Sales Milestones [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payments of milestones											89,000,000.0
Checkpoint [Member] \| Licensing Agreements [Member] \| Jubilant Biosys Ltd [Member] \| Achievement of Certain Preclinical, Clinical Development, and Regulatory Milestones [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payments of milestones											89,000,000.0
Checkpoint [Member] \| Licensing Agreements [Member] \| Jubilant Biosys Ltd [Member] \| Regulatory Approvals to Commercialize the Products [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payments of milestones											$ 59,500,000
Checkpoint [Member] \| Licensing Agreements [Member] \| Collaborative Agreements with TGTX [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Percentage of IND enabling costs and patent expenses																50.00%
Checkpoint [Member] \| Licensing Agreements [Member] \| Collaborative Agreements with TGTX [Member] \| Upon Various Filings for Regulatory Approvals [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payments of milestones																$ 87,200,000
Checkpoint [Member] \| Licensing Agreements [Member] \| Collaborative Agreements with TGTX [Member] \| Completion of Clinical Development Milestones [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payments of milestones																25,500,000
Checkpoint [Member] \| Licensing Agreements [Member] \| Collaborative Agreements with TGTX [Member] \| Achievement of Five Regulatory Approvals [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payments of milestones																61,700,000
Checkpoint [Member] \| Licensing Agreements [Member] \| Collaborative Agreements with TGTX [Member] \| Achievement of Three Sales Milestones [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payments of milestones																89,000,000.0
Checkpoint [Member] \| Licensing Agreements [Member] \| Collaborative Agreements with TGTX [Member] \| Dana Farber Cancer Institute [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue from collaboration agreement																1,000,000.0	1,600,000
Additional Annual License fee								$ 1,000,000.0
Checkpoint [Member] \| Licensing Agreements [Member] \| Collaborative Agreements with TGTX [Member] \| Dana Farber Cancer Institute [Member] \| Completion of Clinical Development Milestones [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payments of milestones								8,400,000
Checkpoint [Member] \| Licensing Agreements [Member] \| Collaborative Agreements with TGTX [Member] \| Dana Farber Cancer Institute [Member] \| Upon the Twelfth Patient Dosed in a Phase 1 Clinical Study [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payments of milestones																925,000
Checkpoint [Member] \| Licensing Agreements [Member] \| Collaborative Agreements with TGTX [Member] \| Jubilant Biosys Ltd [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Upfront fees payment																$ 1,000,000.0
Number of development milestones \| Milestone																3
Revenue from collaboration agreement																$ 100,000	100,000	$ 0
Checkpoint [Member] \| Licensing Agreements [Member] \| Collaborative Agreements with TGTX [Member] \| Jubilant Biosys Ltd [Member] \| Achievement of Five Regulatory Approvals [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Number Of Regulatory Milestones \| Milestone																5
Checkpoint [Member] \| Licensing Agreements [Member] \| Collaborative Agreements with TGTX [Member] \| Jubilant Biosys Ltd [Member] \| Achievement of Three Sales Milestones [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Number of net sales milestones \| Milestone																3
Checkpoint [Member] \| Licensing Agreements [Member] \| Anti-PD-L1 [Member] \| Collaborative Agreements with TGTX [Member] \| Dana Farber Cancer Institute [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Upfront fees payment								500,000
Checkpoint [Member] \| Licensing Agreements [Member] \| Anti-PD-L1 [Member] \| Collaborative Agreements with TGTX [Member] \| Dana Farber Cancer Institute [Member] \| Achievement of Certain clinical Development, Regulatory and First Commercial Sale milestones [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payments of milestones								27,600,000
Checkpoint [Member] \| Licensing Agreements [Member] \| Anti-PD-L1 [Member] \| Collaborative Agreements with TGTX [Member] \| Dana Farber Cancer Institute [Member] \| First Commercial Sales in Specified Territories [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payments of milestones								19,200,000
Checkpoint [Member] \| Licensing Agreements [Member] \| Anti-GITR Antibody [Member] \| Collaborative Agreements with TGTX [Member] \| Dana Farber Cancer Institute [Member] \| Achievement of Certain Sales Milestones [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payments of milestones																$ 60,000,000.0
Checkpoint [Member] \| Licensing Agreements [Member] \| Anti-GITR Antibody [Member] \| Collaborative Agreements with TGTX [Member] \| Dana Farber Cancer Institute [Member] \| Achievement of Certain clinical Development, Regulatory and First Commercial Sale milestones [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payments of milestones								21,500,000
Checkpoint [Member] \| Licensing Agreements [Member] \| Anti-GITR Antibody [Member] \| Collaborative Agreements with TGTX [Member] \| Dana Farber Cancer Institute [Member] \| Completion of Clinical Development Milestones [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payments of milestones								$ 7,000,000.0
Checkpoint [Member] \| Licensing Agreements [Member] \| Anti-GITR Antibody [Member] \| Collaborative Agreements with TGTX [Member] \| Dana Farber Cancer Institute [Member] \| First Commercial Sales in Specified Territories [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payments of milestones																14,500,000
Helocyte [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research and development - licenses acquired																0	450,000
Helocyte [Member] \| Licensing Agreements [Member] \| National Institute of Allergy and Infectious Disease (NIAD) [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Upfront fees payment							$ 500,000
Research and development - licenses acquired																0	500,000
Minimum Annual Royalty Payable							$ 55,000
Payment Of Upfront Fees, Number Of Installments \| installment							3
Helocyte [Member] \| Licensing Agreements [Member] \| National Institute of Allergy and Infectious Disease (NIAD) [Member] \| Achievement of Four Development Milestones [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Additional Minimum Annual Royalty Payable							$ 1,050,000
Helocyte [Member] \| Licensing Agreements [Member] \| National Institutes of Health ("NIH") [Member] \| Achievement of Four Development Milestones [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Number of development milestones \| Milestone												4
Helocyte [Member] \| Licensing Agreements [Member] \| City of Hope (COH) [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Upfront fees payment													$ 45,000
Helocyte [Member] \| Licensing Agreements [Member] \| Triplex [Member] \| City of Hope (COH) [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Upfront fees payment						$ 200,000
Helocyte [Member] \| Licensing Agreements [Member] \| Triplex [Member] \| City of Hope (COH) [Member] \| Achievement of Each Milestones [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payments of milestones						$ 7,500,000
Helocyte [Member] \| Licensing Agreements [Member] \| Triplex [Member] \| City of Hope (COH) [Member] \| Achievement of Certain Sales Milestones [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Number of net sales milestones \| Milestone						3
Payments of milestones						$ 26,000,000.0
Helocyte [Member] \| Licensing Agreements [Member] \| Triplex [Member] \| City of Hope (COH) [Member] \| Financial Milestones [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Number of net sales milestones \| Milestone						3
Number of development milestones \| Milestone						2
Payments of milestones						$ 3,700,000
Helocyte [Member] \| Licensing Agreements [Member] \| Pentameter [Member] \| City of Hope (COH) [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research and development - licenses acquired																0	0
Helocyte [Member] \| Licensing Agreements [Member] \| Pentameter [Member] \| City of Hope (COH) [Member] \| Achievement of Four Development Milestones [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Number of development milestones \| Milestone													4
Payments of milestones													$ 5,500,000
Helocyte [Member] \| Licensing Agreements [Member] \| Pentameter [Member] \| City of Hope (COH) [Member] \| Achievement of Three Sales Milestones [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Number of net sales milestones \| Milestone													3
Payments of milestones													$ 26,000,000.0
Helocyte [Member] \| Licensing Agreements [Member] \| Pentameter [Member] \| City of Hope (COH) [Member] \| First Marketing Approval [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Minimum Annual Royalty Payable													$ 750,000
Cyprium [Member] \| Licensing Agreements [Member] \| National Institutes of Health ("NIH") [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Upfront fees payment									$ 100,000
Research and development - licenses acquired																$ 0	$ 0
Cyprium [Member] \| Licensing Agreements [Member] \| National Institutes of Health ("NIH") [Member] \| Achievement of Certain Sales Milestones [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payments of milestones									1,000,000
Cyprium [Member] \| Licensing Agreements [Member] \| National Institutes of Health ("NIH") [Member] \| Completion of Clinical Development Milestones [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payments of milestones									1,700,000
Cyprium [Member] \| Licensing Agreements [Member] \| National Institutes of Health ("NIH") [Member] \| Redeems a PRV [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payments of milestones									$ 15,000,000
Cyprium [Member] \| Licensing Agreements [Member] \| National Institutes of Health ("NIH") [Member] \| First PRV Sold [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Sales royalties (as a percent)									20.00%
Cyprium [Member] \| Licensing Agreements [Member] \| National Institutes of Health ("NIH") [Member] \| Second PRV Sold [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Sales royalties (as a percent)									15.00%