Nature of Business and Basis of Presentation - Additional Information (Detail)			12 Months Ended
	Sep. 13, 2018 $ / shares shares	Mar. 09, 2017 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) $ / shares shares	Sep. 12, 2018 shares	Jan. 31, 2017 USD ($)
Business And Basis Of Presentation [Line Items]
Repayment of notes payable			$ 1,549,702	$ 212,431
Shares of common stock called by warrants | shares		1,659
Warrants exercise price per share | $ / shares		$ 0.01	$ 5.03
Common stock, par or stated value per share | $ / shares	$ 0.0001		$ 0.0001	$ 0.0001
Common stock, shares authorized | shares	200,000,000		200,000,000	100,000,000	100,000,000
Reverse split	1-for-30
Reverse split conversion ratio	0.03
Merger Agreement [Member}
Business And Basis Of Presentation [Line Items]
Agreement of reorganization and merger date			Jan. 18, 2017
Merger Agreement [Member} | Merger Sub Corp I Inc and Mustang Merger Sub II LLC [Member]
Business And Basis Of Presentation [Line Items]
Business acquisition, percentage of voting interest acquired			100.00%
Convertible Promissory Note Purchase Agreement [Member] | 6% Convertible Notes [Member]
Business And Basis Of Presentation [Line Items]
Notes payable						$ 8,600,000
Notes payable, interest rate						6.00%
Description of second closing			The second closing under the Note Agreement was satisfied in connection with the sale of Series B redeemable convertible preferred stock (“redeemable preferred stock”) that closed on August 16, 2017 (see Note 10).
Convertible Promissory Note Purchase Agreement [Member] | 6% Convertible Notes [Member] | Convertible Promissory Note Purchase Agreement Initial Closing [Member]
Business And Basis Of Presentation [Line Items]
Gross proceeds from notes payable		$ 3,150,630
Repayment of notes payable		196,496
Accrued expenses modified and replaced with convertible notes		$ 881,044