Pension Plan (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Dec. 31, 2018	Dec. 31, 2019	Sep. 30, 2018
Change in benefit obligation:
Benefit obligation at beginning of period	$ 95.8	$ 94.1	$ 105.9
Interest cost	0.7	2.7	2.9
Prior service cost			0.5
Actuarial (gain)/loss		14.1	(8.3)
Benefits paid		(4.2)	(2.6)
Foreign currency translation adjustments		3.7	(2.6)
Benefit obligation at end of period	94.1	110.4	95.8
Change in plan assets:
Fair value of plan assets at beginning of period	101.1	97.4	102.5
Actual gain/(loss) on plan assets		10.3	0.7
Employer contributions		0.2	3.3
Benefits paid		(4.2)	(2.6)
Foreign currency translation adjustments		3.6	(2.8)
Fair value of assets at end of period	$ 97.4	107.3	101.1
Amount recognized in the consolidated balance sheets:
Overfunded (Unfunded) status (non-current)		(3.1)	5.3
Net amount recognized		$ (3.1)	$ 5.3

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.