Stock-based Compensation - Schedule of Information Regarding Restricted Stock Unit Outstanding (Detail) (Restricted Stock Units [Member], USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
RSUs outstanding, Number of Shares	668,056	708,651	407,765	417,923
RSUs vested and expected to vest using estimated forfeiture rates, Number of Shares	583,711	588,170	336,454
RSUs outstanding, Weighted Average Remaining Contractual Life (years)	10 months 28 days	1 year 1 month 2 days	11 months 12 days
RSUs vested and expected to vest using estimated forfeiture rates, Weighted Average Remaining Contractual Life (years)	10 months 21 days	1 year 18 days	11 months 1 day
RSUs outstanding, Aggregate Intrinsic Value	$ 6.9	$ 4.9	$ 2.1
RSUs vested and expected to vest using estimated forfeiture rates, Aggregate Intrinsic Value	6.1	4.0	1.7
RSUs outstanding, Fair Value	$ 6.9	$ 4.9	$ 2.1