Debt (Recourse Debt) (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Long-term debt
Less: current maturities	$ 32,256	$ 69,366
Collateralized debt book value	61,900
Recourse
Long-term debt
Long-term debt, gross	564,225	833,428
Less: current maturities	24,655	68,688
Less: unamortized prepaid debt issuance costs	4,055	5,479
Long-term debt, less current maturities	535,515	759,261
Recourse | Note payable, variable rate (1.70% at December 31, 2021), payable in increasing amounts plus interest, due 2026
Long-term debt
Long-term debt, gross	$ 212,500	225,000
Interest rate of debt instruments	1.70%
Recourse | Note payable, variable rate (1.58% at December 31, 2021), payable in increasing amounts plus interest, due 2026
Long-term debt
Long-term debt, gross	$ 142,500	150,000
Interest rate of debt instruments	1.58%
Recourse | Note payable, variable rate, paid 2021
Long-term debt
Long-term debt, gross	$ 0	145,000
Recourse | Note payable, 4.50%, payable at maturity, due 2034 (a)
Long-term debt
Long-term debt, gross	$ 99,090	102,524
Interest rate of debt instruments	4.50%
Recourse | Finance lease obligations, due serially to 2030 (a)
Long-term debt
Long-term debt, gross	$ 10,135	22,262
Recourse | Note payable, 4.07%, paid 2021
Long-term debt
Long-term debt, gross	$ 0	26,000
Interest rate of debt instruments	4.07%
Recourse | Note payable, 4.85%, payable at maturity, due 2026
Long-term debt
Long-term debt, gross	$ 25,000	25,000
Interest rate of debt instruments	4.85%
Recourse | Note payable, 4.55%, payable at maturity, due 2023
Long-term debt
Long-term debt, gross	$ 24,000	24,000
Interest rate of debt instruments	4.55%
Recourse | Note payable, 3.33%, paid 2021
Long-term debt
Long-term debt, gross	$ 0	22,634
Interest rate of debt instruments	3.33%
Recourse | Note payable, 3.29%, paid 2021
Long-term debt
Long-term debt, gross	$ 0	16,028
Interest rate of debt instruments	3.29%
Recourse | Note payable, 4.50%, payable at maturity, due 2030
Long-term debt
Long-term debt, gross	$ 16,000	16,000
Interest rate of debt instruments	4.50%
Recourse | Note payable, 5.00%, payable at maturity, due 2040
Long-term debt
Long-term debt, gross	$ 14,000	14,000
Interest rate of debt instruments	5.00%
Recourse | Note payable, variable rate, paid 2021
Long-term debt
Long-term debt, gross	$ 0	11,250
Recourse | Industrial revenue bond, variable rate (1.22% at December 31, 2021), payable at maturity, due 2036
Long-term debt
Long-term debt, gross	$ 21,000	21,000
Interest rate of debt instruments	1.22%
Recourse | Debenture bonds, 2.65% to 4.50%, paid 2021
Long-term debt
Long-term debt, gross	$ 0	$ 12,730
Recourse | Debenture bonds, 2.65% to 4.50%, paid 2021 | Minimum
Long-term debt
Interest rate of debt instruments	2.65%
Recourse | Debenture bonds, 2.65% to 4.50%, paid 2021 | Maximum
Long-term debt
Interest rate of debt instruments	4.50%