Long-term Debt - Credit Agreement (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Debt Instrument [Line Items]
Net leverage ratio	3.00
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 300.0
Debt Instrument, Maturity Date	Sep. 20, 2022
Debt Instrument, Basis Spread on Variable Rate	1.50%
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Revolving Credit Facility, Capacity Available for Foreign Revolver Loans	$ 125.0
Line of Credit Facility, Maximum Borrowing Capacity	300.0
Revolving Credit Facility, Amount Outstanding	0.0	$ 0.0
Revolving Credit Facility, Remaining Borrowing Capacity	284.9	284.9
Letters of credit [Member]
Debt Instrument [Line Items]
Letters of Credit, Maximum Borrowing Capacity	40.0
Letters of Credit Outstanding, Amount	15.1	15.1
Revolving credit and term loan facilities [Member]
Debt Instrument [Line Items]
Incremental debt commitments capacity	200.0
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Debt Instrument, Unused Borrowing Capacity, Amount	$ 284.9	$ 284.9