Fortress Biotech, Inc. Quarterly report pursuant to Section 13 or 15(d)

Quarterly report pursuant to Section 13 or 15(d)

Organization and Description of Business - Additional Information (Detail)

Organization and Description of Business - Additional Information (Detail) (USD $)	3 Months Ended		1 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Feb. 28, 2015	Apr. 30, 2015
Organization And Nature Of Business [Line Items]
Share Price	$ 2.73us-gaap_SharePrice
Payments to Acquire Intangible Assets	$ 1,250,000	$ 0
Research And Development In Process	7,439,000us-gaap_ResearchAndDevelopmentInProcess	0us-gaap_ResearchAndDevelopmentInProcess
Stock Issued During Period, Value, Issued for Services	1,000	4,000
Research And Development Expense	1,642,000us-gaap_ResearchAndDevelopmentExpense	4,487,000us-gaap_ResearchAndDevelopmentExpense
Coronado SO [Member] \| Licensing Agreements [Member]
Organization And Nature Of Business [Line Items]
Equity Method Investment, Ownership Percentage			13.00%
Payments for Fees			900,000
Share Price			$ 1.67
Stock Issued During Period, Shares, Other			150,000
Marketability Percentage Of Invested Capital			44.80%
Share-based Compensation Arrangement by Share-based Payment Award, Purchase Price of Common Stock, Percent			30.00%
Stock Issued During Period, Value, Other			200,000
Collaboration Agreement with TGTX [Member]
Organization And Nature Of Business [Line Items]
Payments for Fees	500,000
License and Services Revenue	500,000
Dana Farber Cancer Institute [Member] \| Licensing Agreements [Member]
Organization And Nature Of Business [Line Items]
Payments for Fees	1,000,000
Dana Farber Cancer Institute [Member] \| Restricted Stock Purchase Agreement [Member]
Organization And Nature Of Business [Line Items]
Share Price	$ 0.10
Marketability Percentage Of Invested Capital	44.80%
Share-based Compensation Arrangement by Share-based Payment Award, Purchase Price of Common Stock, Percent	30.00%
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	48 months
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage	25.00%
Research And Development Expense	3,000
Mustang Bio, Inc [Member] \| Agreement With City Of Hope [Member]
Organization And Nature Of Business [Line Items]
Payments to Acquire in Process Research and Development	2,000,000
Journey Medical Corporation [Member]
Organization And Nature Of Business [Line Items]
Research And Development In Process	700,000
Journey Medical Corporation [Member] \| Licensing Agreements [Member]
Organization And Nature Of Business [Line Items]
Payments for Fees	1,200,000
NeuPharma [Member] \| Licensing Agreements [Member]
Organization And Nature Of Business [Line Items]
Payments for Fees	1,000,000
IV Tramadol [Member] \| Licensing Agreements [Member]
Organization And Nature Of Business [Line Items]
Payments for Fees			1,000,000
Payments to Acquire Intangible Assets			2,000,000
TG Therapeutics, Inc [Member] \| Collaboration Agreement with TGTX [Member]
Organization And Nature Of Business [Line Items]
Payments for Fees	500,000
City Of Hope [Member] \| Licensing Agreements [Member]
Organization And Nature Of Business [Line Items]
Share Price	$ 0.26
Stock Issued During Period, Shares, Other	1,000,000
Marketability Percentage Of Invested Capital	44.80%
Share-based Compensation Arrangement by Share-based Payment Award, Purchase Price of Common Stock, Percent	30.00%
Stock Issued During Period, Value, Other	300,000
Scientific Advisory Board [Member]
Organization And Nature Of Business [Line Items]
Stock Issued During Period, Shares, Issued for Services	1,500,000
Stock Issued During Period, Value, Issued for Services	200,000
Subsequent Event [Member] \| Mustang Bio, Inc [Member] \| Agreement With City Of Hope [Member]
Organization And Nature Of Business [Line Items]
Common Stock Representing Additional Milestones Payments Due				10.00%
Subsequent Event [Member] \| City Of Hope [Member] \| Licensing Agreements [Member]
Organization And Nature Of Business [Line Items]
Payments for Fees				2,000,000