Debt (Details Textual) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$ 375.0
Line of Credit Facility, Remaining Borrowing Capacity	275.5
Additional term loan
Line of Credit Facility [Line Items]
Maximum borrowing capacity	300.0
Letter of Credit
Line of Credit Facility [Line Items]
Letters of Credit Outstanding, Amount	$ 27.2	$ 27.3
Revolving Credit Facility
Line of Credit Facility [Line Items]
Variable commitment fee	0.20%
Short-term Debt [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Remaining Borrowing Capacity	$ 355.4