Defined Benefit Plans - Amounts Recognized in Consolidated Balance Sheets (Detail) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Accrued benefit liability	$ (218.4)	$ (216.9)
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Current benefit payment liability	(1.1)	(1.0)
Accrued benefit liability	(204.7)	(199.4)
Net amount recognized	(205.8)	(200.4)
Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Current benefit payment liability	(2.0)	(2.6)
Accrued benefit liability	(13.6)	(17.5)
Net amount recognized	$ (15.6)	$ (20.1)