Retirement Plans - Reconciliation of Benefit Obligation, Plan Assets and Funded Status of Plans (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Pension Benefits
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of year	$ 1,138.0	$ 1,060.7
Service cost	1.2	1.0	$ 1.0
Interest cost	20.4	27.4	33.3
Plan participants' contributions	0.0	0.0
Medicare reimbursements	0.0	0.0
Actuarial (gain) loss	(31.8)	86.0
Plan amendments and other	2.6	0.1
Settlements	(2.9)	(6.6)
Foreign currency translation	(2.0)	15.0
Benefits paid	(47.6)	(45.6)
Benefit obligation at end of year	1,077.9	1,138.0	1,060.7
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	1,090.2	985.6
Actual return on assets	44.8	132.1
Settlements	(2.9)	(6.6)
Employer contributions	5.0	9.2
Company reimbursements	0.0	0.0
Medicare reimbursements	0.0	0.0
Plan participants' contributions	0.0	0.0
Foreign currency translation	(2.6)	15.5
Benefits paid	(47.6)	(45.6)
Fair value of plan assets at end of year	1,086.9	1,090.2	985.6
Total net pension and OPEB asset (liability) recognized as of December 31	9.0	(47.8)
OPEB
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of year	293.4	289.8
Service cost	0.0	0.0	0.0
Interest cost	4.2	7.3	10.1
Plan participants' contributions	6.2	7.8
Medicare reimbursements	7.2	7.9
Actuarial (gain) loss	(70.6)	8.1
Plan amendments and other	0.0	0.0
Settlements	0.0	0.0
Foreign currency translation	0.0	0.0
Benefits paid	(25.9)	(27.5)
Benefit obligation at end of year	214.5	293.4	289.8
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	237.2	227.7
Actual return on assets	22.9	21.0
Settlements	0.0	0.0
Employer contributions	0.0	7.2
Company reimbursements	0.0	(6.9)
Medicare reimbursements	7.2	7.9
Plan participants' contributions	6.2	7.8
Foreign currency translation	0.0	0.0
Benefits paid	(25.9)	(27.5)
Fair value of plan assets at end of year	247.6	237.2	$ 227.7
Total net pension and OPEB asset (liability) recognized as of December 31	$ 33.1	$ (56.2)