Acquisitions - Summary of Pre-tax Merger Related Costs (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs, Legal Fees	$ 0.3	$ 0.5
Business Combination, Acquisition Related Costs, Employee Expense	0.6	0.1
Business Combination, Acquisition Related Costs, Technology and Contract Termination	0.8	1.5
Business Combination, Acquisition Related Costs, Other Expenses	0.6	0.2
Acquisition related expenses	$ 2.3	$ 2.3	$ 2.3