Stockholders' Equity - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-based compensation expense	$ 2.2	$ 2.5	$ 12.3	$ 12.9
Stock-based compensation expense realized tax benefits from the excess of deductible amounts over expense recognized	$ 0.5	$ 0.5	$ 2.7	$ 2.0
Additional common shares issued under deferred and stock compensation arrangements			533,812
Treasury shares purchased	1,371,339		1,371,339
Treasury shares retired			731,355