Stockholders' Equity - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-based compensation expense	$ 2.5	$ 2.7	$ 12.9	$ 11.2
Stock-based compensation expense realized tax benefits from the excess of deductible amounts over expense recognized	$ 0.5	$ 1.0	$ 2.0	$ 2.5
Additional common shares issued under deferred and stock compensation arrangements			541,252