Debt - Short-Term Borrowings (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016
Line of Credit Facility [Line Items]
Short-term borrowings	$ 216,604	$ 140,465
Revolving Credit Facility
Line of Credit Facility [Line Items]
Short-term borrowings	216,604	$ 140,465
Minimum
Line of Credit Facility [Line Items]
Short-term borrowings	112,292		$ 105,014
Maximum
Line of Credit Facility [Line Items]
Short-term borrowings	$ 229,782		$ 311,506