Pension Plans - Reconciliations of Plan Benefit Obligation, Fair Value of Plan Assets and Funded Status of Pension Plans (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
Dec. 31, 2021	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at January 1		$ 411.6	$ 454.7
Interest cost		7.5	6.7	$ 8.4
Settlement gain		(5.9)	0.0
Actuarial gains		(102.7)	(30.4)
Exchange difference		(37.0)	(4.0)
Benefits paid		(15.3)	(15.4)
Benefit obligation at December 31	$ 411.6	258.2	411.6	454.7
Change in plan assets
Fair value of plan assets at January 1		423.4	403.9
Actual return on assets		(81.6)	20.4
Exchange difference		(40.4)	(3.7)
Contributions from employer		0.4	18.2
Benefits paid		(15.2)	(15.4)
Settlement loss		(5.9)	0.0
Fair value of plan assets at December 31	423.4	280.7	423.4	403.9
Funded status
Net benefit surplus / (obligation)	11.8	22.5	11.8
U.K.
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at January 1		362.9	404.0
Interest cost		6.2	5.6	7.0
Settlement gain		0.0	0.0
Actuarial gains		(93.7)	(29.6)
Exchange difference		(37.0)	(4.0)
Benefits paid	(12.7)	(12.8)	(13.1)
Benefit obligation at December 31	362.9	225.6	362.9	404.0
Change in plan assets
Fair value of plan assets at January 1		376.6	358.9
Actual return on assets		(71.2)	16.3
Exchange difference		(40.4)	(3.7)
Contributions from employer		0.4	18.2
Benefits paid		(12.8)	(13.1)
Settlement loss		0.0	0.0
Fair value of plan assets at December 31	376.6	252.6	376.6	358.9
Funded status
Net benefit surplus / (obligation)	13.7	27.0	13.7
U.S. / other
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at January 1		48.7	50.7
Interest cost		1.3	1.1	1.4
Settlement gain		(5.9)	0.0
Actuarial gains		(9.0)	(0.8)
Exchange difference		0.0	0.0
Benefits paid		(2.5)	(2.3)
Benefit obligation at December 31	48.7	32.6	48.7	50.7
Change in plan assets
Fair value of plan assets at January 1		46.8	45.0
Actual return on assets		(10.4)	4.1
Exchange difference		0.0	0.0
Contributions from employer		0.0	0.0
Benefits paid		(2.4)	(2.3)
Settlement loss		(5.9)	0.0
Fair value of plan assets at December 31	46.8	28.1	46.8	$ 45.0
Funded status
Net benefit surplus / (obligation)	$ (1.9)	$ (4.5)	$ (1.9)

Amount of increase (decrease) in plan assets of defined benefit plan from actual return (loss) determined by change in fair value of plan assets adjusted for contributions, benefit payments, and other expenses.

Name:	us-gaap_DefinedBenefitPlanActualReturnOnPlanAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of gain (loss) from change in actuarial assumptions which (increases) decreases benefit obligation of defined benefit plan. Assumptions include, but are not limited to, interest, mortality, employee turnover, salary, and temporary deviation from substantive plan.