Leases - Schedule of components of leased cost (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019
Operating Leased Assets [Line Items]
Operating lease cost	$ 63.0	$ 181.4
Depreciation and amortization	0.9	1.7
Interest expense	0.2	0.6
Net lease cost	64.1	183.7
Cost of services - lease type contracts
Operating Leased Assets [Line Items]
Operating lease cost	61.4	177.5
General and administrative expenses
Operating Leased Assets [Line Items]
Operating lease cost	$ 1.6	$ 3.9