Changes in Accumulated Other Comprehensive Income (Loss) (Additional Information) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Actuarial gains (losses), net of tax	$ (0.6)	$ (6.1)	$ 5.9
Actuarial (losses) gains, tax expense (benefit)	(0.4)	(3.7)	3.6
Amortization of actuarial losses, net of tax	0.5	3.5	0.7
Amortization of actuarial losses, tax expense (benefit)	$ (0.3)	(2.1)	$ (0.4)
Pension settlement costs, net of tax		3.0
Pension settlement costs, tax expense (benefit)		$ (1.9)