Acquisitions - Summary of Pre-tax Merger Related Costs (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Business Combinations [Abstract]
Legal and Professional Fees	$ 0.1	$ 2.4	$ 0.8	$ 3.0
Employee Expenses	1.4	0.0	8.2	0.1
Technology Conversion and Contract Termination	1.5	0.5	8.7	2.0
Other	0.8	0.2	1.9	0.3
Acquisition related expenses	$ 3.8	$ 3.1	$ 19.6	$ 5.4