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

Related Party Transactions - Schedule of dividend or equity fee recorded by the Company (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Dividends Payable, Current	$ 0	$ 0
Aevitas Inc [Member]
Dividends Payable Date Of Record Description	January 1
Dividends Payable, Current	$ 6	6
Caelum Bio sciences Inc [Member]
Dividends Payable Date Of Record Description	January 1
Dividends Payable, Current	$ 0	462
Cellvation Inc [Member]
Dividends Payable Date Of Record Description	January 1
Dividends Payable, Current	$ 7	5
Checkpoint [Member]
Dividends Payable Date Of Record Description	January 1
Dividends Payable, Current	$ 2,510	1,748
Cyprium Bio sciences Inc [Member]
Dividends Payable Date Of Record Description	January 1
Dividends Payable, Current	$ 5	3
Helocyte Inc [Member]
Dividends Payable Date Of Record Description	January 1
Dividends Payable, Current	$ 131	167
Mustang Bio, Inc [Member]
Dividends Payable Date Of Record Description	January 1
Dividends Payable, Current	$ 4,923	2,085
Tamid [Member]
Dividends Payable Date Of Record Description	January 1
Dividends Payable, Current	$ 7	15
Fortress Biotech Inc [Member]
Dividends Payable, Current	$ (7,589)	$ (4,491)