Property, Equipment, and Software - Allocation of Depreciation and Amortization Expense between Cost of Services and Selling, General and Administrative Expenses (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Property, Plant and Equipment [Line Items]
Total depreciation and amortization	$ 12.3	$ 9.4	$ 24.5	$ 18.8
Cost of services
Property, Plant and Equipment [Line Items]
Total depreciation and amortization	11.4	8.6	22.3	17.5
Selling, general and administrative
Property, Plant and Equipment [Line Items]
Total depreciation and amortization	$ 0.9	$ 0.8	$ 2.2	$ 1.3