Stockholders' Equity - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-based compensation expense	$ 2.3	$ 2.9	$ 10.1	$ 10.4
Stock-based compensation expense realized tax benefits from the excess of deductible amounts over expense recognized	$ 1.0	$ 0.2	$ 2.2	$ 1.5
Additional common shares issued under deferred and stock compensation arrangements			443,964
Treasury shares retired			731,355