Pensions and Post-Retirement Benefit Plans - Components of Net Periodic Benefit Cost for Pension Plans and Other Benefit Plans (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1.7	$ 2.0	$ 2.7
Interest cost	11.0	10.9	11.8
Expected return on plan assets	(10.5)	(12.0)	(13.9)
Amortization of prior service cost	0.0	(0.3)	(0.2)
Amortization of net loss	2.2	6.6	4.0
Settlements and curtailments	4.4	(0.8)	0.0
Net periodic benefit cost	8.8	6.4	4.4
Other Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	0.1	0.1	0.1
Interest cost	0.4	0.4	0.5
Expected return on plan assets	0.0	0.0	0.0
Amortization of prior service cost	0.0	(0.1)	(0.2)
Amortization of net loss	(0.4)	(0.3)	0.0
Settlements and curtailments	0.0	0.0	0.0
Net periodic benefit cost	$ 0.1	$ 0.1	$ 0.4