Revenue (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($)
Deferred contract costs and capitalized sales commissions
Capitalized Contract Cost [Line Items]
Capitalized contract cost, gross	$ 89.2
Capitalized sales commissions to selling, general and administrative expenses
Capitalized Contract Cost [Line Items]
Capitalized contract cost, amortization	11.1
Other deferred contract costs as a reduction of revenue
Capitalized Contract Cost [Line Items]
Capitalized contract cost, amortization	$ 5.9
Collection Service Line
Capitalized Contract Cost [Line Items]
Standard contract term	3 years