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
	Mar. 31, 2020	Mar. 31, 2019
Property, Plant and Equipment [Line Items]
Total depreciation and amortization	$ 12.2	$ 9.4
Cost of services
Property, Plant and Equipment [Line Items]
Total depreciation and amortization	10.9	8.9
Selling, general and administrative
Property, Plant and Equipment [Line Items]
Total depreciation and amortization	$ 1.3	$ 0.5