Debt Short-Term Borrowings (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Line of Credit Facility [Line Items]
Short-term borrowings	$ 104,978	$ 66,342
Short-term debt average amount outstanding	$ 119,000	67,000
Weighted average interest rate	1.40%
Revolving Credit Facility
Line of Credit Facility [Line Items]
Short-term borrowings	$ 104,978	$ 66,342
Interest rate during the period	1.31%	1.52%
Minimum
Line of Credit Facility [Line Items]
Short-term borrowings	$ 35,981	$ 25,550
Maximum
Line of Credit Facility [Line Items]
Short-term borrowings	$ 184,188	$ 111,912