Stock Options - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of unissued common stock available for grant under the plans	2.3
Share-based compensation expense	$ 7.2	$ 5.9
Cash received from stock options exercised	2.6	0.5
Performance-Based Unit | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares which will vest after achievement of goals	0
Performance-Based Unit | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares which will vest after achievement of goals	1.5
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	2.1	2.3
Total unrecognized compensation cost	12.0
Unrecognized compensation cost, Weighted-average recognition period	2 years 9 months 18 days
Aggregate weighted-average grant-date fair value of units granted	12.6	4.7
Aggregate weighted-average grant-date fair value of units vested	2.0	4.2
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	5.1	3.6
Total intrinsic value of options exercised	4.5	0.6
Total unrecognized compensation cost	$ 6.3
Unrecognized compensation cost, Weighted-average recognition period	2 years 1 month 6 days