Debt - Short-Term Borrowings (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Line of Credit Facility [Line Items]
Short-term borrowings	$ 180,000		$ 169,643
Interest expense, net	1,411	$ 797
Revolving Credit Facility
Line of Credit Facility [Line Items]
Short-term borrowings	180,000		$ 169,643
Minimum
Line of Credit Facility [Line Items]
Short-term borrowings	140,000	112,292
Maximum
Line of Credit Facility [Line Items]
Short-term borrowings	$ 234,000	$ 166,501