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

Accrued Liabilities and other Long-Term Liabilities (Narrative) (Details)

Accrued Liabilities and other Long-Term Liabilities (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 18, 2020	Jun. 29, 2020	Jul. 22, 2019
Long-term notes payable, net (Journey)	$ 51,677	$ 77,436
Amortization of interest discount	5,622	3,321
Notes payable, short-term	0	7,220
Ximino [Member]
Initial discount for imputed interest					$ 2,300
Ximino [Member] \| Journey [Member]
Initial discount for imputed interest		2,300
Long-term notes payable, net (Journey)		$ 4,700
Effective interest rate used to calculated imputed interest discount (in percent)		11.96%
Period of effective interest rate considered for calculation of imputed interest discount (in years)		5 years
Amortization of interest discount	600	$ 300
Notes payable, short-term	2,000
Oral Acne Product (Isotretinoin) [Member]
Initial discount for imputed interest				$ 300
Oral Acne Product (Isotretinoin) [Member] \| Journey [Member]
Initial discount for imputed interest	300
Long-term notes payable, net (Journey)	$ 3,700
Effective interest rate used to calculated imputed interest discount (in percent)	4.00%
Period of effective interest rate considered for calculation of imputed interest discount (in years)	3 years
Amortization of interest discount	$ 100
Notes payable, short-term	500
Anti-itch Product [Member]
Initial discount for imputed interest			$ 100
Anti-itch Product [Member] \| Journey [Member]
Initial discount for imputed interest	100
Long-term notes payable, net (Journey)	$ 3,700
Effective interest rate used to calculated imputed interest discount (in percent)	4.25%
Period of effective interest rate considered for calculation of imputed interest discount (in years)	3 years
Notes payable, short-term	$ 2,800