Long-Term Debt And Other Long-Term Liabilities (Other Long-Term Liabilities) (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021	Dec. 31, 2020
Debt Disclosure [Abstract]
Asset retirement obligation (ARO) liability	$ 24,939	$ 25,688	$ 23,843	$ 23,356
Workers' compensation	7,673	7,925	$ 11,735	$ 10,164
Contract liability	864	1,788
Separation benefit plans	1,776	2,022
Gas balancing liability	1,082	1,090
Other liabilities	36,334	38,513
Current portion of other long-term liabilities	4,537	5,574
Total other long-term liabilities	$ 31,797	$ 32,939