Stockholders' Equity and Dilutive Equity Instruments - Additional Information (Detail) - $ / shares	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Stockholders Equity Note [Line Items]
Shares issuable upon exercise of warrants	0	108,044
In-the-money Warrants and Restricted Stock Awards and Units
Stockholders Equity Note [Line Items]
Incremental "in-the-money" warrants, and restricted stock awards and units	3,997,084	4,521,727
Out-of-the-money Warrants
Stockholders Equity Note [Line Items]
Warrants outstanding	5,923,399	5,062,089
Out-of-the-money Warrants | Series A Warrants
Stockholders Equity Note [Line Items]
Warrants exercise prices	$ 57.06	$ 57.06
Out-of-the-money Warrants | Series B Warrants
Stockholders Equity Note [Line Items]
Warrants exercise prices	62.28	62.28
Out-of-the-money Warrants | GLF Equity Warrants
Stockholders Equity Note [Line Items]
Warrants exercise prices	$ 100	$ 100