Additional Balance Sheet Information (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Accounts receivable, net
Trade accounts	$ 130,729	$ 227,835
Joint interest accounts	1,388	2,245
Income taxes receivable	5,797	3,612
Other accounts	1,440	6,515
Accounts receivable, gross	139,354	240,207
Allowance for doubtful accounts	(1,000)	(1,198)
Accounts receivable, net	138,354	239,009
Inventories
Tubular goods and well equipment	17,750	10,675
Natural gas in storage	2,651	3,281
Other accounts	22	70
Inventory, net	20,423	14,026
Other assets
Deferred compensation plan	13,282	13,115
Debt issuance cost	22,850	17,349
Other accounts	65	65
Other assets	36,197	30,529
Accounts payable
Trade accounts	37,627	54,949
Natural gas purchases	3,138	2,407
Royalty and other owners	75,759	97,298
Accrued capital costs	87,551	222,426
Taxes other than income	8,818	16,806
Drilling advances	81	88
Other accounts	5,659	6,102
Accounts payable current	218,633	400,076
Accrued liabilities
Employee benefits	12,871	22,815
Taxes other than income	11,663	7,128
Interest payable	30,143	30,677
Other accounts	2,788	3,049
Accrued liabilities	57,465	63,669
Other liabilities
Deferred compensation plan	30,130	28,932
Other accounts	4,876	10,675
Other liabilities	$ 35,006	$ 39,607