Related Party Transactions - THL (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Related Party Transaction [Line Items]
Related party expenses, net	$ 12.1	$ 12.6	$ 16.9
Operating expenses
Related Party Transaction [Line Items]
Related party expenses, net	12.1	12.3
Thomas H. Lee Partners, LP
Related Party Transaction [Line Items]
Software and software-related purchases			1.1
Thomas H. Lee Partners, LP | Operating expenses
Related Party Transaction [Line Items]
Related party expenses, net			$ 1.3
Thomas H. Lee Partners, LP
Related Party Transaction [Line Items]
Software and software-related purchases	0.0	0.0
Thomas H. Lee Partners, LP | Operating expenses
Related Party Transaction [Line Items]
Related party expenses, net	$ 0.0	$ 0.3