Credit Arrangements Short Term Debt (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2016
Short-term Debt [Line Items]
Short-term debt payable to non-affiliates	$ 15,000	$ 0
Short-Term Debt December 21st [Member]
Short-term Debt [Line Items]
Short-term debt payable to non-affiliates	$ 10,000
Line of Credit Facility, Interest Rate During Period	0.55%
Short-Term Debt December 30th [Member]
Short-term Debt [Line Items]
Short-term debt payable to non-affiliates	$ 5,000
Line of Credit Facility, Interest Rate During Period	0.46%