Debt (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016
Debt Instrument [Line Items]
Short-term debt	$ 255,000	$ 29,000	$ 274,002
Long-term debt
Total current maturities of long-term debt	56,144	47,545	54,044
Total long-term debt, less current maturities	365,971	397,065	402,360
Recourse
Debt Instrument [Line Items]
Short-term debt	255,000	29,000	274,002
Long-term debt
Total current maturities of long-term debt	56,144	47,545	54,044
Total long-term debt, less current maturities	$ 365,971	$ 397,065	$ 402,360