Acquisitions - Summary of Pre-tax Merger Related Costs (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Business Combinations [Abstract]
Legal and Professional Fees	$ 0.4	$ 0.0	$ 0.7	$ 0.5
Employee Expenses	6.2	0.0	6.8	0.1
Technology Conversion and Contract Termination	6.4	0.0	7.2	1.5
Other	0.5	0.0	1.1	0.2
Acquisition related expenses	$ 13.5	$ 0.0	$ 15.8	$ 2.3