Additional Balance Sheet Information - Certain Balance Sheet Amounts (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Accounts receivable, net
Trade accounts	$ 209,200	$ 362,973
Other accounts	1,007	668
Receivables gross current	210,207	363,641
Allowance for doubtful accounts	(1,184)	(1,238)
Accounts receivable, net	209,023	362,403
Other assets
Deferred compensation plan	18,381	14,699
Debt issuance cost	8,938	4,572
Income taxes receivable	0	8,165
Operating lease right-of-use assets	35,916
Other accounts	56	61
Other assets	63,291	27,497
Accounts payable
Trade accounts	21,663	30,033
Royalty and other owners	36,191	61,507
Accrued transportation	55,586	50,540
Accrued capital costs	40,337	43,207
Taxes other than income	16,971	19,824
Income taxes payable	0	1,134
Other accounts	19,063	35,694
Accounts payable current	189,811	241,939
Accrued liabilities
Employee benefits	22,727	21,761
Taxes other than income	3,850	1,472
Operating lease liabilities	3,124
Other accounts	1,589	1,994
Accrued liabilities	31,290	25,227
Other liabilities
Deferred compensation plan	27,012	25,780
Operating lease liabilities	32,677
Other accounts	8,595	34,391
Other liabilities	$ 68,284	$ 60,171