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

Quarterly report pursuant to Section 13 or 15(d)

Collaboration and Stock Purchase Agreements (Narrative) (Details)

Collaboration and Stock Purchase Agreements (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands, shares in Millions			3 Months Ended		6 Months Ended
	Feb. 24, 2021	Feb. 08, 2019	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Cash and cash equivalents			$ 274,992	$ 183,278	$ 274,992	$ 183,278	$ 233,351
Collaboration revenue			2,400	$ 0	3,200	0
Accumulated deficit			(495,117)		(495,117)		$ (482,760)
Cyprium [Member] \| Sentynl Therapeutics, Inc [Member]
Upfront fees payment	$ 8,000
Payments of milestones	$ 12,000
Percentage of ownership over any FDA priority review voucher	100.00%
Collaboration revenue			2,400		3,200	$ 0
Avenue [Member]
Cash and cash equivalents			1,100		1,100
Accumulated deficit			$ (75,200)		(75,200)
SPMA [Member] \| Minimum [Member] \| Avenue [Member] \| InvaGen [Member]
Percentage of common shares acquired in the Stock Purchase Transaction for the rights to exist		75.00%
SPMA [Member] \| Maximum [Member] \| Avenue [Member] \| InvaGen [Member]
Business Combination, possible Interim financing		$ 7,000
FDA approval of the NDA [Member] \| Cyprium [Member] \| Sentynl Therapeutics, Inc [Member]
Payments of milestones	$ 9,000
Achievement of Certain Sales Milestones [Member] \| Maximum [Member] \| Cyprium [Member] \| Sentynl Therapeutics, Inc [Member]
Payments of milestones	255,000
Strategic Transaction, First Stage [Member] \| SPMA [Member] \| Avenue [Member] \| InvaGen [Member]
Sale of stock, number of shares issued		5.8
Sale of stock, price per share		$ 6.00
Sale of Stock, Consideration Received on Transaction		$ 35,000
Sale of stock, ownership percentage after the transaction		33.30%
Strategic Transaction, Second Stage [Member] \| SPMA [Member] \| Avenue [Member] \| InvaGen [Member]
Sale of Stock, Consideration Received on Transaction		$ 180,000
Completion of Clinical Development Milestones [Member] \| Cyprium [Member] \| Sentynl Therapeutics, Inc [Member]
Payments of milestones	$ 3,000
IV Tramadol [Member] \| FDA approval of the NDA [Member] \| Avenue [Member]
Payments of milestones					$ 5,000