Benefit Plans - Amounts Recorded in Consolidated Balance Sheets (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Non-current liabilities	$ (96.4)	$ (90.0)
Accumulated benefit obligation	107.1	275.0
Pension plans
Defined Benefit Plan Disclosure [Line Items]
Current liabilities	(5.3)	(28.3)
Non-current liabilities	(75.8)	(68.9)
Benefit obligations in excess of the fair value of plan assets	(81.1)	(97.2)
Other post-retirement plans
Defined Benefit Plan Disclosure [Line Items]
Current liabilities	(1.7)	(1.7)
Non-current liabilities	(12.9)	(13.2)
Benefit obligations in excess of the fair value of plan assets	$ (14.6)	$ (14.9)