Debt (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015
Debt Instrument [Line Items]
Short-term debt	$ 274,002	$ 16,990	$ 311,660
Long-term debt
Total current maturities of long-term debt	54,044	27,786	19,037
Total long-term debt, less current maturities	402,360	436,208	323,258
Nonrecourse
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	274,002	16,990	311,660
Long-term debt
Total current maturities of long-term debt	54,044	27,786	19,037
Total long-term debt, less current maturities	$ 402,360	$ 436,208	$ 323,258