Amounts Recognized in Consolidated Balance Sheets (Detail) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Other assets	$ 6.4	$ 5.4
Accrued benefit cost	(158.7)	(84.6)
Net amount recognized	(152.3)	(79.2)
Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Accrued benefit cost	(7.0)	(6.8)
Net amount recognized	$ (7.0)	$ (6.8)