Fair Value Measurements - Reconciliation of Liabilities Measured at Fair Value Using Level 3 Significant Unobservable Inputs (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract]
Balance, beginning of period	$ 2,342
Issuance of common stock warrants		$ 885
Initial recognition of obligation to issue common stock to Eiccose		1,457
Change in fair value of common stock warrants and obligation to issue common stock to Eiccose	369
Settlement of warrant liability upon exercise of common stock warrants	(1,050)
Settlement of Eiccose obligation upon issuance of common stock	$ (1,661)
Balance, end of period		$ 2,342