Debt (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014
Debt Instrument [Line Items]
Short-term debt	$ 141,250	$ 2,166	$ 27,000
Long-term debt
Total current maturities of long-term debt	27,188	76,415	89,387
Total long-term debt, less current maturities	417,279	298,638	300,220
Nonrecourse
Long-term debt
Total current maturities of long-term debt	0	0	3,100
Total long-term debt, less current maturities	0	0	2,515
Recourse
Debt Instrument [Line Items]
Short-term debt	141,250	2,166	27,000
Long-term debt
Total current maturities of long-term debt	27,188	76,415	86,287
Total long-term debt, less current maturities	$ 417,279	$ 298,638	$ 297,705