Benefit Plans - Amounts Recorded in Consolidated Balance Sheets (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Non-current liabilities	$ (90.0)	$ (96.4)
Accumulated benefit obligation	275.0	470.4
Pension plans
Defined Benefit Plan Disclosure [Line Items]
Current liabilities	(28.3)	(6.1)
Non-current liabilities	(68.9)	(84.9)
Benefit obligations in excess of the fair value of plan assets	(97.2)	(91.0)
Other post-retirement plans
Defined Benefit Plan Disclosure [Line Items]
Current liabilities	(1.7)	(1.9)
Non-current liabilities	(13.2)	(15.6)
Benefit obligations in excess of the fair value of plan assets	$ (14.9)	$ (17.5)