Additional Balance Sheet Information - Schedule of Additional Balance Sheet Information (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Accounts receivable, net
Trade accounts	$ 221,515	$ 215,511
Joint interest accounts	1,916	467
Other accounts	852	1,312
Accounts receivable, gross	224,283	217,290
Allowance for doubtful accounts	(1,456)	(1,286)
Accounts receivable, net	222,827	216,004
Other assets
Deferred compensation plan	16,671	14,966
Debt issuance costs	5,427	7,990
Income taxes receivable	5,321	0
Other accounts	227	56
Other assets	27,646	23,012
Accounts payable
Trade accounts	34,869	7,815
Natural gas purchases	36,115	4,299
Royalty and other owners	33,206	39,207
Accrued transportation	47,934	51,433
Accrued capital costs	33,150	31,130
Taxes other than income	11,787	16,801
Deposits received for asset sales	0	81,500
Other accounts	66,562	5,860
Accounts payable	263,623	238,045
Accrued liabilities
Employee benefits	12,970	20,645
Taxes other than income	1,708	550
Asset retirement obligations	1,000	4,952
Other accounts	(225)	1,294
Accrued liabilities	15,453	27,441
Other liabilities
Deferred compensation plan	27,835	29,145
Other accounts	34,052	10,578
Other liabilities	$ 61,887	$ 39,723