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

Sponsored Research Agreements - Additional Information (Detail) - USD ($)	1 Months Ended		3 Months Ended		6 Months Ended
	Jun. 30, 2017	Feb. 17, 2017	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Checkpoint Therapeutics, Inc [Member]
Reimbursement Of Cost Recognized As Revenue			$ 200,000	$ 200,000	$ 400,000	$ 500,000
Helocyte Inc [Member] \| Pentamer Sponsored Research Agreement [Member]
Payments For Research And Development Expenses					12,000
Payment of Upfront Milestone Fees	$ 1,500,000
Helocyte Inc [Member] \| Pep Vax [Member]
Payments For Research And Development Expenses					200,000	1,000,000
Helocyte Inc [Member] \| Triplex [Member]
Payments For Research And Development Expenses			500,000	0	1,000,000	1,000,000
Mustang Bio, Inc [Member]
Research And Development Expense Payable Milestone Payment	$ 2,000,000		2,000,000		2,000,000
Payments For Research And Development Expenses			500,000	$ 500,000	1,000,000	$ 1,000,000
City Of Hope [Member] \| AR IL-13 License [Member]
Research And Development Expense			11,000		1,000,000
Payment of Upfront Milestone Fees		$ 10,000
Revenue Recognition Milestone Method Payments Due Over Three Years		200,000
Revenue Recognition Milestone Method Payments Due		100,000
City Of Hope [Member] \| AR CD123 License [Member]
Research And Development Expense			$ 22,000		$ 600,000
Payment of Upfront Milestone Fees		20,000
Revenue Recognition Milestone Method Payments Due Over Three Years		200,000
Revenue Recognition Milestone Method Payments Due		$ 100,000