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

Changes in Fair Value of Financial Instruments (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at December 31, 2014	$ 4,160
Purchases	0
Change in fair value of investment	(215)
Balance at March 31, 2015	3,945
CB Pharma Acquisitions Corp [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at December 31, 2014	3,910
Purchases	0
Change in fair value of investment	(215)
Balance at March 31, 2015	3,695
Short-term Investments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at December 31, 2014	0
Purchases	0
Change in fair value of investment	0
Balance at March 31, 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
Purchases	0
Change in fair value of investment	0
Balance at March 31, 2015	$ 250