Debt (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2011
Long-term debt
Total current maturities of long-term debt	$ 30,342	$ 32,208	$ 42,783
Total long-term debt, less current maturities	220,417	238,885	263,218
Recourse [Member]
Long-term debt
Total current maturities of long-term debt	30,182	32,051	39,948
Total long-term debt, less current maturities	219,662	238,088	250,804
Nonrecourse [Member]
Long-term debt
Total current maturities of long-term debt	160	157	2,835
Total long-term debt, less current maturities	$ 755	$ 797	$ 12,414