Long-Term Debt And Other Long-Term Liabilities (Other Long-Term Liabilities) (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021	Jun. 30, 2021	Dec. 31, 2020
Debt Disclosure [Abstract]
Asset retirement obligation (ARO) liability	$ 25,406	$ 25,688	$ 23,172	$ 23,356
Workers' compensation	7,483	7,925	$ 11,730	$ 10,164
Contract liability	748	1,788
Separation benefit plans	1,658	2,022
Gas balancing liability	1,090	1,090
Other liabilities	36,385	38,513
Current portion of other long-term liabilities	5,009	5,574
Total other long-term liabilities	$ 31,376	$ 32,939