Debt (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015
Debt Instrument [Line Items]
Short-term debt (Note 4)	$ 179,404	$ 16,990	$ 141,250
Long-term debt
Total current maturities of long-term debt	53,720	27,786	27,188
Total long-term debt, less current maturities	398,746	436,208	417,279
Nonrecourse
Debt Instrument [Line Items]
Short-term debt (Note 4)	0	0	0
Long-term debt
Total current maturities of long-term debt	0	0	0
Total long-term debt, less current maturities	0	0	0
Recourse
Debt Instrument [Line Items]
Short-term debt (Note 4)	179,404	16,990	141,250
Long-term debt
Total current maturities of long-term debt	53,720	27,786	27,188
Total long-term debt, less current maturities	$ 398,746	$ 436,208	$ 417,279