Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Income Tax Disclosure [Abstract]
Effective tax rate for income from continuing operations	24.40%	30.20%	32.50%	36.30%
Discrete tax charges (benefits)	$ (1.2)	$ 1.0	$ (1.2)	$ 1.0