Unaudited Condensed Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Cash flows from operating activities
Net income	$ 463,897	$ 474,778
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion, amortization and accretion	448,639	314,367
Property impairments	119,793	65,778
Change in fair value of derivatives	(125,787)	(349,652)
Stock-based compensation	18,998	13,305
Provision for deferred income taxes	266,618	290,738
Dry hole costs	8,063	98
(Gain) loss on sale of assets, net	213	(67,024)
Other, net	2,466	2,275
Changes in assets and liabilities:
Accounts receivable	(100,542)	18,375
Inventories	4,658	(10,212)
Prepaid expenses and other	(6,526)	2,952
Accounts payable trade	21,678	(21,661)
Revenues and royalties payable	12,920	4,477
Accrued liabilities and other	16,018	32,241
Other noncurrent assets and liabilities	5,839	(5)
Net cash provided by operating activities	1,156,945	770,830
Cash flows from investing activities
Exploration and development	(1,823,215)	(1,778,808)
Purchase of producing crude oil and natural gas properties	(9,311)	(63,263)
Purchase of other property and equipment	(18,545)	(32,230)
Proceeds from sale of assets	894	100,809
Net cash used in investing activities	(1,850,177)	(1,773,492)
Cash flows from financing activities
Revolving credit facility borrowings	440,000	1,239,000
Repayment of revolving credit facility	(1,035,000)	(1,060,000)
Proceeds from issuance of Senior Notes	1,479,375	787,000
Proceeds from other debt	0	22,000
Repayment of other debt	(969)	(628)
Debt issuance costs	(2,231)	(4,083)
Repurchase of equity grants	(3,259)	(5,094)
Exercise of stock options	0	60
Net cash provided by financing activities	877,916	978,255
Net change in cash and cash equivalents	184,684	(24,407)
Cash and cash equivalents at beginning of period	35,729	53,544
Cash and cash equivalents at end of period	$ 220,413	$ 29,137