Condensed Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Current assets:
Cash and cash equivalents	$ 91,507	$ 35,729
Receivables:
Crude oil and natural gas sales	644,401	468,650
Affiliated parties	16,923	12,410
Joint interest and other, net	356,897	356,111
Derivative assets	17,380	18,389
Inventories	55,272	46,743
Deferred and prepaid taxes	21,514	365
Prepaid expenses and other	9,287	8,386
Total current assets	1,213,181	946,783
Net property and equipment, based on successful efforts method of accounting	10,112,506	8,105,269
Net debt issuance costs and other	72,424	55,726
Noncurrent derivative assets	22,177	32,231
Total assets	11,420,288	9,140,009
Current liabilities:
Accounts payable trade	906,688	687,310
Revenues and royalties payable	310,137	261,856
Payables to affiliated parties	8,341	6,069
Accrued liabilities and other	197,264	153,454
Derivative liabilities	41,590	12,999
Current portion of asset retirement obligations	2,054	2,227
Current portion of long-term debt	1,997	1,950
Total current liabilities	1,468,071	1,125,865
Long-term debt, net of current portion	4,439,825	3,537,771
Other noncurrent liabilities:
Deferred income tax liabilities	1,641,589	1,262,576
Asset retirement obligations, net of current portion	47,667	44,944
Noncurrent derivative liabilities	157	2,173
Other noncurrent liabilities	2,366	2,981
Total other noncurrent liabilities	1,691,779	1,312,674
Commitments and contingencies (Note 7)
Shareholders’ equity:
Preferred stock, $0.01 par value; 25,000,000 shares authorized; no shares issued and outstanding	0	0
Common stock, $0.01 par value; 500,000,000 shares authorized; 185,665,535 shares issued and outstanding at September 30, 2013; 185,604,681 shares issued and outstanding at December 31, 2012	1,857	1,856
Additional paid-in capital	1,252,353	1,226,835
Retained earnings	2,566,403	1,935,008
Total shareholders’ equity	3,820,613	3,163,699
Total liabilities and shareholders’ equity	$ 11,420,288	$ 9,140,009