Stock-Based Compensation - Schedule of Information Regarding Standard and Market Condition Based Stock Options Outstanding (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Standard Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options outstanding, Number of Shares	3,596,533	3,486,157	3,227,167	3,155,631
Options vested and expected to vest using estimated forfeiture rates, Number of Shares	3,452,487	3,319,308	2,994,044
Options exercisable, Number of Shares	2,252,744	2,023,024	1,774,546
Options outstanding, Weighted Average Exercise Price (in dollars per share)	$ 8.45	$ 8.30	$ 7.78	$ 6.65
Options vested and expected to vest using estimated forfeiture rates, Weighted Average Exercise Price (in dollars per share)	8.36	8.21	7.61
Options exercisable, Weighted Average Exercise Price (in dollars per share)	$ 7.59	$ 7.18	$ 6.67
Options outstanding, Weighted Average Remaining Contractual Life (years)	4 years 2 months 23 days	4 years 10 months 6 days	5 years 5 months 16 days
Options vested and expected to vest using estimated forfeiture rates, Weighted Average Remaining Contractual Life (years)	4 years 1 month 27 days	4 years 9 months 18 days	5 years 4 months 28 days
Options exercisable, Weighted Average Remaining Contractual Life (years)	3 years 6 months 21 days	4 years 3 months 4 days	4 years 11 months 12 days
Options outstanding, Aggregate Intrinsic Value	$ 12.5	$ 6.6	$ 9.9
Options vested and expected to vest using estimated forfeiture rates, Aggregate Intrinsic Value	12.3	6.6	9.6
Options exercisable, Aggregate Intrinsic Value	$ 9.9	$ 6.0	$ 7.5
Market Condition Based Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options outstanding, Number of Shares	200,000	50,000	0
Options vested and expected to vest using estimated forfeiture rates, Number of Shares	184,125	45,430
Options exercisable, Number of Shares	0	0
Options outstanding, Weighted Average Exercise Price (in dollars per share)	$ 9.05	$ 11.94	$ 0.00
Options vested and expected to vest using estimated forfeiture rates, Weighted Average Exercise Price (in dollars per share)	9.12	11.94
Options exercisable, Weighted Average Exercise Price (in dollars per share)	$ 0.00	$ 0.00
Options outstanding, Weighted Average Remaining Contractual Life (years)	5 years 11 months 1 day	6 years 1 month 24 days
Options vested and expected to vest using estimated forfeiture rates, Weighted Average Remaining Contractual Life (years)	5 years 10 months 24 days	6 years 1 month 24 days
Options exercisable, Weighted Average Remaining Contractual Life (years)	0 years	0 years
Options outstanding, Aggregate Intrinsic Value	$ 0.5	$ 0.0
Options vested and expected to vest using estimated forfeiture rates, Aggregate Intrinsic Value	0.5	0.0
Options exercisable, Aggregate Intrinsic Value	$ 0.0	$ 0.0