Stockholders' Equity - Additional Information (Detail)

v3.20.1

Stockholders' Equity - Additional Information (Detail) - USD ($)								1 Months Ended				12 Months Ended
	Feb. 11, 2019	Jan. 01, 2019	Jul. 03, 2018	Apr. 05, 2018	Jan. 01, 2018	Nov. 30, 2017	Sep. 30, 2015	Nov. 30, 2019	Apr. 30, 2019	Mar. 31, 2018	Nov. 30, 2017	Dec. 31, 2019	Dec. 31, 2018	Aug. 16, 2019	Jul. 23, 2019	Mar. 29, 2019	Jul. 13, 2018	Jun. 30, 2018	Dec. 31, 2017	Dec. 15, 2017	Oct. 26, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Based compensation, authorized number of shares												13,750,535
Stock-based compensation												$ 13,188,000	$ 15,012,000
Stock-based compensation expense												$ 13,188,000	$ 15,012,000
Common Stock, Par or Stated Value Per Share												$ 0.001	$ 0.001
Share Price			$ 3.04
Class of Warrant or Right, Exercise Price of Warrants or Rights																$ 3.47
Stock Issued During Period, Value, Issued for Services							$ 600,000					$ 500,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross												125,000
Capital Units, Authorized												100,000,000
Proceeds from issuance of Common stock	$ 13,100,000
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Stock Options												$ 11,900,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized													7,700,000
Share-based Compensation												$ 13,188,000	$ 15,012,000
Stock Issued During Period, Shares, New Issues			164,473
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period												290,000	490,000
Payments of Stock Issuance Costs										$ 41,400,000		$ 578,000	$ 0
Adjustments To Additional Paid In Capital At Market Offering Costs												$ 1,800,000
Preferred Stock, Shares Outstanding												1,341,167	1,000,000
Preferred Stock, Shares Authorized												15,000,000	15,000,000
Preferred Stock, par value												$ 0.001	$ 0.001
Preferred Stock, Value, Issued												$ 1,000	$ 1,000
Preferred Stock, Shares Issued												1,341,167	1,000,000
Dividends Payable, Amount Per Share																			$ 0.5839375
Preferred Stock, Liquidation Preference Per Share												$ 25.00	$ 25.00
Proceeds from Issuance of Preferred Stock and Preference Stock												$ 6,038,000	$ 154,000
Payments for Fees						$ 100,000					$ 2,100,000
Percentage of Placement of Agent Fee											3.00%	1.00%
Common Stock, Shares, Outstanding												74,027,425	57,845,447
Common Stock, Value, Issued												$ 74,000	$ 58,000
Revenue from Contract with Customer, Including Assessed Tax												$ 34,921,000	$ 23,376,000
Common Stock, Shares, Issued												74,027,425	57,845,447
Proceeds From Issuance Of Preferred Stock, At The Market Offering												$ 812,000	$ 0
Common Stock Shares Available For Future Issuance Value															$ 38,300,000
Long-term incentive plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cash bonus																		$ 500,000
Employee Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee Stock Purchase Plan to eligible employees, Reckoning fair value percentage during offering period												85.00%
Common Stock issued in connection with the first ESPP offering												454,515
Stock-based compensation												$ 100,000	$ 200,000
Common Stock, Capital Shares Reserved for Future Issuance												545,485
Plan 2013 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Based compensation, authorized number of shares													10,000,000
Revenue from Contract with Customer, Including Assessed Tax													$ 2,300,000
Plan 2007 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Based compensation, authorized number of shares													6,000,000
Longterm Incentive Program [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense												$ 1,400,000	$ 1,300,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested in Period, Fair Value												$ 600,000	2,300,000
Capital Units, Authorized												100,000,000
Share-based Compensation												$ 1,400,000	$ 1,300,000
Plan 2017 and 2013 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Based compensation, shares available for issuance																						16,000,000
Plan 2007 And 2013 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Based compensation, shares available for issuance												2,249,465
Series A Preferred Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares Issued, Price Per Share						$ 25.00					$ 25.00
Preferred Stock, Shares Authorized																					5,000,000
Preferred Stock, par value																					$ 0.001
Preferred Stock, Dividend Rate, Percentage												9.375%
Dividends Payable, Amount Per Share																			$ 0.299479	$ 2.34375
Preferred Stock, Liquidation Preference Per Share												$ 25.00
Issuance Of Preferred Stock For At Market Offering, In Shares												39,292
Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common Stock issued in connection with the first ESPP offering												98,007	110,856
Shares Issued, Price Per Share												$ 1.88	$ 2.50
Issuance of Common Stock for At the Market Offering in shares												11,798,468	2,914,410
Adjustments To Additional Paid In Capital At Market Offering Costs												$ 300,000	$ 300,000
Common Stock [Member] | Market Offering [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Proceeds from issuance of Common stock												$ 15,100,000	$ 7,300,000
Issuance of Common Stock for At the Market Offering in shares												8,000,000	2,900,000
Common Stock [Member] | 2019 At The Market Offering [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Proceeds from issuance of Common stock												$ 5,600,000
Issuance of Common Stock for At the Market Offering in shares												3,800,000
Average Price Per Share												$ 1.49
Agents Commission, Percentage												3.00%
Payments for Commissions												$ 200,000
Preferred Stock [Member] | IPO [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights								39,375
Preferred Stock, Dividend Rate, Percentage								9.375%
Average Price Per Share								$ 20
Issuance Of Preferred Stock For Public Offering								262,500
Additional shares								39,375
Proceeds from issuance of preferred stock								$ 6,000,000
Preferred Stock [Member] | 2018 Preferred ATM
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Preferred Stock, Dividend Rate, Percentage				9.375%
Issuance Of Preferred Stock For At Market Offering, In Shares												39,292
Proceeds From Issuance Of Preferred Stock, At The Market Offering												$ 800,000
Average Price Per Share												$ 20.67
Agents Commission, Percentage												7.00%
Payments for Commissions												$ 24,000
Senior Vice President [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Issued During Period, Value, Issued for Services												2,600,000	$ 2,300,000
Mustang Bio, Inc [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common Stock Shares Available For Future Issuance Value												20,900,000
Marketable Securities														$ 75,000,000			$ 75,000,000
Mustang Bio, Inc [Member] | Common Stock [Member] | Market Offering [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Proceeds from issuance of Common stock												$ 22,500,000
Issuance of Common Stock for At the Market Offering in shares												3,500,000
Average Price Per Share												$ 6.42
Agents Commission, Percentage												3.00%
Proceeds From Issuance Of Common Stock Net of Issuance Costs												$ 22,000,000
Mustang Bio, Inc [Member] | Common Stock [Member] | IPO [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights									1,031,250
Stock Issued During Period, Value, New Issues									$ 6,875,000		$ 31,600,000
Average Price Per Share									$ 4.00
Additional shares									1,031,250
Proceeds From Issuance Of Common Stock Net of Issuance Costs									$ 29,500,000
Checkpoint [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares Issued, Price Per Share										$ 4.35
Proceeds from issuance of Common stock								$ 19,600,000		$ 20,800,000		$ 8,000,000	$ 8,000,000
Stock Issued During Period, Shares, New Issues								15,400,000		5,290,000		2,273,189	1,841,774
Stock Issued During Period, Value, New Issues										$ 23,000,000
Payments of Stock Issuance Costs										$ 2,200,000
Maximum Authorized Amount Of Shares To Be Sold						$ 100,000,000					$ 100,000,000
Average Price Per Share								$ 1.27				$ 3.52	$ 4.33
Proceeds From Issuance Of Common Stock Net of Issuance Costs								$ 17,600,000				$ 7,800,000	$ 7,700,000
Underwriting Discounts And Offering Expenses								$ 2,000,000
Dr Rosenwald [Member] | Longterm Incentive Program [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period		648,204			586,429
Research and Development Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation												2,800,000	5,300,000
General and Administrative Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation												10,400,000	9,700,000
Restricted Stock Awards and Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation												$ 11,500,000	$ 13,900,000
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Deferred Compensation Arrangement with Individual, Shares Issued												230,000	230,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Granted in Period, Fair Value												$ 1,400,000	$ 6,600,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period												1,546,408	1,721,802
Stock Issued During Period, Value, Restricted Stock Award, Gross												$ 2,000,000	$ 3,300,000
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Granted in Period, Fair Value												$ 400,000	1,800,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period												227,083
Restricted Stock Units (RSUs) [Member] | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition												4 years 9 months 18 days
Restricted Stock Units (RSUs) [Member] | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition												2 years 1 month 6 days
Restricted Stock Units (RSUs) [Member] | Mustang Bio, Inc [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Adjustments To Additional Paid In Capital At Market Offering Costs												$ 500,000
Restricted Stock Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period												395,869
Options to Purchase Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense												$ 300,000	100,000
Share-based Compensation												$ 300,000	$ 100,000