Long-Term Debt And Other Long-Term Liabilities (Other Long-Term Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017	Dec. 31, 2016
Long-term debt and other long-term liabilites [Abstract]
ARO liability	$ 64,208		$ 69,444	$ 70,170
Workers' compensation	12,738		13,340
Capital lease obligations	11,380		15,224
Contract liability	9,881		0
Separation benefit plans	8,814		6,524
Deferred compensation plan	5,132		5,390
Gas balancing liability	3,331		3,283
Other liabilities	115,484		113,205
Current portion of other long-term liabilities	14,250	$ 15,750	13,002
Other long-term liabilities	$ 101,234	$ 109,940	$ 100,203