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

Debt and Interest (Interest Expense) (Details)

Debt and Interest (Interest Expense) (Details) - USD ($) $ in Thousands		12 Months Ended
	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Interest expense, interest		$ 9,704	$ 8,528
Amortization of fees		5,622	3,321
Interest expense, Total		15,326	11,849
Unamortized debt discount fees		8,323	5,086
Opus Credit Facility (2019 Notes) [Member]
Debt Instrument [Line Items]
Interest expense, interest		710	1,113
Amortization of fees		0	336
Interest expense, Total		710	1,449
Letter of Credit [Member]
Debt Instrument [Line Items]
Interest expense, interest		34	60
Amortization of fees		0	0
Interest expense, Total		34	60
IDB Note Payable [Member]
Debt Instrument [Line Items]
Interest expense, interest		246	356
Amortization of fees		0
Interest expense, Total		246	356
2017 Subordinated Note Financing [Member]
Debt Instrument [Line Items]
Interest expense, interest		2,870	4,220
Amortization of fees		1,890	1,381
Interest expense, Total		4,760	5,601
Unamortized debt discount fees		1,200
2018 Venture Notes [Member]
Debt Instrument [Line Items]
Interest expense, interest		1,253	1,737
Amortization of fees		1,000	639
Interest expense, Total		2,253	2,376
Unamortized debt discount fees		300
Mustang Horizon Notes [Member]
Debt Instrument [Line Items]
Interest expense, interest	$ 100	1,585	1,042
Amortization of fees		2,321	710
Interest expense, Total		3,906	1,752
Unamortized debt discount fees		1,800
Debt prepayment penalties	$ 600	600
Oaktree Note [Member]
Debt Instrument [Line Items]
Interest expense, interest		2,311	0
Amortization of fees		411	0
Interest expense, Total		2,722	0
NSC Note [Member]
Debt Instrument [Line Items]
Interest expense, interest		697	0
Amortization of fees		0	255
Interest expense, Total		697	255
Other Debt [Member]
Debt Instrument [Line Items]
Interest expense, interest			0
Amortization of fees		0	0
Interest expense, Total			$ 0
Interest expense (income)		$ (2)