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) $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Change in fair value of warrant liability	$ 139
Ending balance	3,047
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	2,908
Change in fair value of warrant liability	139
Ending balance	$ 3,047