Long-Term Debt And Other Long-Term Liabilities (Other Long-Term Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Long-term debt and other long-term liabilites [Abstract]
ARO liability	$ 66,627	$ 64,208	$ 69,444
Workers' compensation	11,510	12,738
Finance lease obligations	7,379	11,380
Contract liability	7,061	9,881
Separation benefit plans	10,122	8,814
Deferred compensation plan	6,180	5,132
Gas balancing liability	3,838	3,331
Other liabilities	112,717	115,484
Current portion of other long-term liabilities	17,376	14,250
Other long-term liabilities	$ 95,341	$ 101,234