Retirement Plans and Other Post-Retirement Benefits - Schedule of Change in Benefit Obligation and Plan Assets (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Change in Plan Assets
Fair value of plan assets at beginning of year	$ 333.2
Fair value of plan assets at end of year		$ 333.2
Pension Benefits [Member]
Change in Benefit Obligation
Balance at beginning of year	332.2	347.0
Service cost	1.3	2.3	$ 2.0
Interest cost	11.5	13.3	13.7
Plan amendments	(0.2)	0.1
Transfers from Discontinued Operations	4.3	25.7
Actuarial (gain)/loss	29.2	(10.6)
Special termination benefits	1.3
Benefits paid	(22.3)	(45.1)
Curtailment	(1.9)
Settlement/transfer	(309.5)
Effect of currency rate changes	(0.2)	(0.5)
Balance at end of year	45.7	332.2	347.0
Change in Plan Assets
Fair value of plan assets at beginning of year	333.2	372.8
Actual return on plan assets	44.1	(22.4)
Total contributions	2.2	2.2
Transfers from Discontinued Operations	5.7	25.7
Benefits paid	(22.3)	(45.1)
Settlement/transfer	(309.5)
Fair value of plan assets at end of year	53.4	333.2	372.8
Funded status at end of year	7.7	1.0
Other Benefits [Member]
Change in Benefit Obligation
Balance at beginning of year	9.2	9.7
Service cost		0.1	0.1
Interest cost	0.3	0.5	0.4
Participant contributions	0.9	1.2
Transfers from Discontinued Operations		4.3
Actuarial (gain)/loss	(0.3)	(3.1)
Benefits paid	(3.0)	(3.5)
Curtailment	(0.6)
Balance at end of year	6.5	9.2	$ 9.7
Change in Plan Assets
Total contributions	3.0	3.5
Benefits paid	(3.0)	(3.5)
Funded status at end of year	$ (6.5)	$ (9.2)