Stock Options - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of unissued common stock available for grant under the plans	2.6
Share-based compensation expense	$ 10.6	$ 10.8
Cash received from stock options exercised	3.3	4.5
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	4.2	2.7
Total unrecognized compensation cost	8.9
Unrecognized compensation cost, Weighted-average recognition period	2 years 3 months 18 days
Aggregate weighted-average grant-date fair value of units granted	12.7	5.0
Aggregate weighted-average grant-date fair value of units vested	2.7	4.3
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	6.4	8.1
Total intrinsic value of options exercised	4.6	5.7
Total unrecognized compensation cost	$ 4.0
Unrecognized compensation cost, Weighted-average recognition period	2 years