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

Non-Controlling Interests - Summary Of Non-controlling Interests in Consolidated Entities (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Noncontrolling Interest [Line Items]
Issuance of common stock to non-controlling interest holders	$ 513
Net loss attributed to non-controlling interest	479	0
Non-controlling interests in consolidated entities	34us-gaap_MinorityInterest		0us-gaap_MinorityInterest
Mustang Therapeutics, Inc [Member]
Noncontrolling Interest [Line Items]
Issuance of common stock to non-controlling interest holders	260
Net loss attributed to non-controlling interest	(226)
Non-controlling interests in consolidated entities	34
Checkpoint Therapeutics, Inc [Member]
Noncontrolling Interest [Line Items]
Issuance of common stock to non-controlling interest holders	3
Net loss attributed to non-controlling interest	(93)
Non-controlling interests in consolidated entities	(90)
Coronado SO Co, Inc [Member]
Noncontrolling Interest [Line Items]
Issuance of common stock to non-controlling interest holders	250
Net loss attributed to non-controlling interest	(160)
Non-controlling interests in consolidated entities	$ 90