Stockholders' Equity - Summary of Restricted Stock Unit Activity (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) shares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
RSUs outstanding at December 31, 2016, Number of Shares	321,816
RSUs awarded, Number of Shares	12,600
RSUs released, Number of Shares	(112,917)
RSUs forfeited, Number of Shares	(141,327)
RSUs outstanding at December 31, 2017, Number of Shares	80,172
RSUs vested and expected to vest at December 31, 2017, Number of Shares	80,172
RSUs outstanding at December, 31, 2017, Weighted Average Remaining Contractual Term	10 months 24 days
RSUs vested and expected to vest at December 31, 2017, Weighted Average Remaining Contractual Term	10 months 24 days
RSUs outstanding at December 31, 2017, Aggregate Intrinsic Value | $	$ 1,315
RSUs vested and expected to vest at December 31, 2017, Aggregate Intrinsic Value | $	$ 1,315