Fair Value of Financial Instruments - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Change in fair value of Level 3 financial liabilities			$ (6,739)	$ (1,646)
Two Thousand Sixteen And Two Thousand Seventeen Private Placement Warrants
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Change in fair value of Level 3 financial liabilities	$ 2,300		$ (6,700)
2016 Placement Warrant
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Change in fair value of Level 3 financial liabilities		$ (1,600)		$ (1,600)