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

Changes in Fair Value of Financial Instruments (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2015 USD ($)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at December 31, 2014	$ 4,160
Change in fair value of investment	(65)
Balance at September 30, 2015	4,095
CB Pharma Acquisitions Corp [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at December 31, 2014	3,910
Change in fair value of investment	(65)
Balance at September 30, 2015	3,845
Short-term Investments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at December 31, 2014	0
Change in fair value of investment	0
Balance at September 30, 2015	0
Other Long-term Investments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at December 31, 2014	250
Change in fair value of investment	0
Balance at September 30, 2015	$ 250