Additional Balance Sheet Information - Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Accounts receivable, net
Trade accounts	$ 116,772	$ 227,835
Joint interest accounts	2,013	2,245
Income taxes receivable	4,323	3,612
Other accounts	2,557	6,515
Receivables gross current	121,342	236,595
Allowance for doubtful accounts	(1,113)	(1,198)
Accounts receivable, net	120,229	235,397
Inventories
Tubular goods and well equipment	2,364	3,281
Natural gas in storage	14,655	10,675
Other accounts	30	70
Inventory, net	17,049	14,026
Other assets
Deferred compensation plan	12,921	13,115
Debt issuance cost	23,732	17,349
Other accounts	64	65
Other assets	36,717	30,529
Accounts payable
Trade accounts	30,038	54,949
Natural gas purchases	2,231	2,407
Royalty and other owners	75,106	97,298
Accrued capital costs	27,479	222,426
Taxes other than income	14,628	16,806
Other accounts	10,925	6,190
Accounts payable current	160,407	400,076
Accrued liabilities
Employee benefits	13,870	22,815
Taxes other than income	5,073	7,128
Interest payable	30,222	30,677
Other accounts	5,980	3,049
Accrued liabilities	24,923	32,992
Other liabilities
Deferred compensation plan	22,371	28,932
Other accounts	3,653	10,675
Other liabilities	$ 26,024	$ 39,607