Schedule of Changes in Benefit Obligations, Plan Assets and Funded Status of Defined Benefit Pension and Post-Retirement Benefit Plans (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Change in projected benefit obligations (PBO)
Participant contributions
Plan amendments
Change in fair value of plan assets
Plan assets at beginning of year		873.8
Actual return on plan assets
Participant contributions
Plan assets at end of year		775.3	873.8
Prior service cost
Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation (ABO) at December 31			921.8
Change in projected benefit obligations (PBO)
PBO at beginning of year		(922.7)	(895.8)
Service cost		(2.0)	(1.8)	(1.8)
Interest cost		(28.9)	(30.0)	(30.6)
Actuarial loss including assumption changes		61.2	(54.3)
Benefits paid		58.6	59.2
PBO at end of year		(833.8)	(922.7)	(895.8)
Change in fair value of plan assets
Plan assets at beginning of year		874.8	787.0
Actual return on plan assets		(39.3)	116.5
Contribution by the company		0.6	30.5
Benefits paid		(58.6)	(59.2)
Plan assets at end of year		777.5	874.8	787.0
Funded status		(56.3)	(47.9)
Current liabilities		(7.1)	(0.5)
Non-current liabilities		(49.2)	(47.4)
Net pension liability at end of year	[1]	(56.3)	(47.9)
Net actuarial loss (gain)		468.9	451.8
Prior service cost			(0.5)
Total recognized in accumulated other comprehensive loss		468.9	451.3
Post-Retirement Benefits
Change in projected benefit obligations (PBO)
PBO at beginning of year		(7.6)	(6.6)
Service cost		(0.2)	(0.1)	(0.1)
Interest cost		(0.3)	(0.3)	(0.2)
Participant contributions		(0.1)	(0.1)
Actuarial loss including assumption changes		0.6	(1.1)
Benefits paid		0.6	0.6
PBO at end of year		(7.0)	(7.6)	$ (6.6)
Change in fair value of plan assets
Contribution by the company		0.5	0.4
Participant contributions		0.1	0.1
Benefits paid		(0.6)	(0.5)
Funded status		(7.0)	(7.6)
Current liabilities		(0.5)	(0.3)
Non-current liabilities		(6.5)	(7.3)
Net pension liability at end of year		(7.0)	(7.6)
Net actuarial loss (gain)		(1.4)	(0.8)
Prior service cost		(2.2)	(2.6)
Total recognized in accumulated other comprehensive loss		$ (3.6)	$ (3.4)

[1] In addition, the Company has a liability for a foreign pension plan of $0.2 million at December 31, 2018 and 2017.