Stock-Based Compensation - Schedule of Information Regarding Restricted Stock Units Outstanding (Detail) - RSUs outstanding - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
RSUs outstanding, number of Shares	427,192	487,423	564,891	668,056
RSUs vested and expected to vest using estimated forfeiture rates, number of shares	349,759	414,934	502,411
RSUs outstanding, weighted average remaining contractual life (years)	11 months 4 days	10 months 24 days	10 months 2 days
RSUs vested and expected to vest using estimated forfeiture rates, weighted average remaining contractual life (years)	9 months 18 days	10 months 13 days	9 months 18 days
RSUs outstanding, aggregate intrinsic value	$ 4.5	$ 5.7	$ 5.3
RSUs vested and expected to vest using estimated forfeiture rates, aggregate intrinsic value	3.7	4.8	4.8
RSUs outstanding, fair value	$ 4.5	$ 5.7	$ 5.3