Acquisitions - Summary of Pre-tax Merger Related Costs (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs, Legal Fees	$ 2.4		$ 3.0
Business Combination, Acquisition Related Costs, Employee Expense	0.0		0.1
Business Combination, Acquisition Related Costs, Technology and Contract Termination	0.5		2.0
Business Combination, Acquisition Related Costs, Other Expenses	0.2		0.3
Acquisition related expenses	$ 3.1	$ 13.0	$ 5.4	$ 23.9