Stock-Based Compensation - Schedule of Information Regarding Restricted Stock Units Outstanding (Detail) - Restricted Stock Units - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
RSUs outstanding, Number of Shares	487,423	564,891	668,056	708,651
RSUs vested and expected to vest using estimated forfeiture rates, Number of Shares	414,934	502,411	583,711
RSUs outstanding, Weighted Average Remaining Contractual Life (years)	10 months 24 days	10 months 2 days	10 months 28 days
RSUs vested and expected to vest using estimated forfeiture rates, Weighted Average Remaining Contractual Life (years)	10 months 13 days	9 months 18 days	10 months 21 days
RSUs outstanding, Aggregate Intrinsic Value	$ 5.7	$ 5.3	$ 6.9
RSUs vested and expected to vest using estimated forfeiture rates, Aggregate Intrinsic Value	4.8	4.8	6.1
RSUs outstanding, Fair Value	$ 5.7	$ 5.3	$ 6.9