Commitments and Contingencies - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2017
Loss Contingencies [Line Items]
Closed-ended terms for guarantees		9 years
Maximum potential future payments on guarantees		$ 37.5
Contingent liabilities, current		80.4	$ 88.5
Contingent liabilities, non-current		33.7	29.4
Errors and Omissions (E&O) claims and other claims
Loss Contingencies [Line Items]
Contingent liabilities		42.9	54.1
Workers' compensation
Loss Contingencies [Line Items]
Contingent liabilities		71.1	63.8
Indemnification assets
Loss Contingencies [Line Items]
Loss contingency, receivable		5.4	18.2
Insurance recoverable
Loss Contingencies [Line Items]
Loss contingency, receivable		17.8	17.6
Other Current Liabilities
Loss Contingencies [Line Items]
Deferred lease incentive liabilities		8.9	6.0
Other Non-Current Liabilities
Loss Contingencies [Line Items]
Deferred lease incentive liabilities		$ 42.8	$ 49.2
Scenario, Forecast | Indemnification assets
Loss Contingencies [Line Items]
Cash payout	$ 5.4