Debt (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015	Sep. 30, 2015
Debt Instrument [Line Items]
Short-term debt	$ 0	$ 16,990	$ 82,801
Long-term debt
Total current maturities of long-term debt	51,520	27,786	26,989
Total long-term debt, less current maturities	395,559	436,208	413,561
Recourse
Debt Instrument [Line Items]
Short-term debt	0	16,990	82,801
Long-term debt
Total current maturities of long-term debt	51,520	27,786	26,989
Total long-term debt, less current maturities	$ 395,559	$ 436,208	$ 413,561