Additional Balance Sheet Information - Certain Balance Sheet Amounts (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Accounts receivable, net
Trade accounts	$ 215,301	$ 209,200
Other accounts	462	1,007
Receivables gross current	215,763	210,207
Allowance for doubtful accounts	(1,039)	(1,184)
Accounts receivable, net	214,724	209,023
Other assets
Deferred compensation plan	22,510	18,381
Debt issuance cost	6,875	8,938
Operating Lease, Right-of-Use Asset	$ 33,741	$ 35,916
Operating Lease, Right-of-Use Asset [Extensible List]	us-gaap:OtherAssets	us-gaap:OtherAssets
Other accounts	$ 85	$ 56
Other assets	63,211	63,291
Accounts payable
Trade accounts	12,896	21,663
Royalty and other owners	37,243	36,191
Accrued transportation	52,238	55,586
Accrued capital costs	37,872	40,337
Taxes other than income	13,736	16,971
Other accounts	8,096	19,063
Accounts payable current	162,081	189,811
Accrued liabilities
Employee benefits	14,270	22,727
Taxes other than income	3,026	3,850
Operating lease liabilities	$ 3,991	$ 3,124
Operating Lease, Liability, Current [Extensible List]	us-gaap:AccountsPayableAndAccruedLiabilitiesCurrent	us-gaap:AccountsPayableAndAccruedLiabilitiesCurrent
Other accounts	$ 1,087	$ 1,589
Accrued liabilities	22,374	31,290
Other liabilities
Deferred compensation plan	30,581	27,012
Operating lease liabilities	$ 29,628	$ 32,677
Operating Lease, Liability, Noncurrent [Extensible List]	us-gaap:OtherLiabilitiesNoncurrent	us-gaap:OtherLiabilitiesNoncurrent
Other accounts	$ 21,069	$ 8,595
Other liabilities	$ 81,278	$ 68,284