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

Quarterly report pursuant to Section 13 or 15(d)

Debt and Interest- Additional Information (Detail)

Debt and Interest- Additional Information (Detail) - USD ($)		1 Months Ended			6 Months Ended
	May 01, 2017	Jun. 30, 2017	May 31, 2017	Mar. 17, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Feb. 13, 2014
Debt [Line Items]
Warrant exercise price		$ 4.02			$ 4.02
Debt discount recorded		$ 4,723,000			$ 4,723,000		$ 2,009,000
Notes Payable		$ 46,954,000			$ 46,954,000		$ 28,215,000
Maximum [Member]
Debt [Line Items]
Warrant exercise price		$ 4.75			$ 4.75
Israel Discount Bank Of New York [Member]
Debt [Line Items]
Debt Instrument, Face Amount								$ 15,000,000
Notes Payable		$ 14,900,000			$ 14,900,000
Debt Instrument, Collateral Amount		15,000,000			15,000,000
Opus Credit Facility [Member]
Debt [Line Items]
Class Of Warrant Or Right Discount On Warrant		1,600,000			1,600,000
Warrants and Rights Outstanding		$ 9,500,000			$ 9,500,000
NSC 2017 Note [Member]
Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage						8.00%
Debt Instrument, Face Amount						$ 3,250,000
Debt Instrument, Maturity Date, Description					Each Note is due on the third anniversary of its issuance, provided that the Company may extend the maturity date for two one-year periods in its sole discretion.
Paid-in-Kind Interest,Percentage						7.00%
Line of Credit Facility, Current Borrowing Capacity						$ 50,000,000
Percentage Of Placement Agent Fee				10.00%	10.00%
Warrants on Sale Price of Note,Percentage		10.00%		10.00%	10.00%
Class of Warrant or Right, Number of Securities Called by Warrants or Rights		508,505			508,505
NSC 2017 Note [Member] \| First Closing [Member]
Debt [Line Items]
Debt discount recorded		$ 200,000			$ 200,000
Proceeds from Fees Received					$ 325,400
NSC 2017 Note [Member] \| Secoud Closing [Member]
Debt [Line Items]
Warrant exercise price	$ 3.65
Proceeds from Notes Payable	$ 8,600,000
Proceeds from Fees Received	$ 900,000
Class of Warrant or Right, Number of Securities Called by Warrants or Rights	234,438	87,946			87,946
NSC 2017 Note [Member] \| Third Closing [Member]
Debt [Line Items]
Warrant exercise price			$ 3.61
Proceeds from Notes Payable			$ 5,300,000
Proceeds from Fees Received			$ 500,000
Class of Warrant or Right, Number of Securities Called by Warrants or Rights			147,806
NSC 2017 Note [Member] \| Fourth Closing [Member]
Debt [Line Items]
Warrant exercise price		$ 4.75			$ 4.75
Proceeds from Notes Payable		$ 1,800,000
Proceeds from Fees Received		$ 200,000
Class of Warrant or Right, Number of Securities Called by Warrants or Rights		38,315			38,315
NSC 2017 Note [Member] \| Maximum [Member]
Debt [Line Items]
Debt Instrument, Face Amount						$ 40,000,000