Debt and Fair Value of Financial Instruments - Schedule of Roll Forward of Warrant Liability Classified as Level 3 and Measured at Fair Value on a Recurring Basis (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Change in fair value of warrant liability	$ 2,085	$ 2,224
Ending balance	9,004	9,004
Fair Value, Measurements, Recurring [Member] | Basis of Fair Value Measurements, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Warrants issued		6,780
Change in fair value of warrant liability		2,224
Ending balance	$ 9,004	$ 9,004