Income Taxes - Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefit, beginning of period	$ 742
Gross increases — current year tax positions	198	$ 130
Gross increases — prior year tax positions		612
Unrecognized tax benefit, end of period	$ 940	$ 742