CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $)	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Net income (loss)	$ 170,935,000		$ (54,249,000)		$ 215,416,000
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
(Gain) loss on divestiture activity	(27,974,000)		27,018,000		(220,676,000)
Depletion, depreciation, amortization, and asset retirement obligation liability accretion	822,872,000		727,877,000		511,103,000
Exploratory dry hole expense	5,846,000		20,861,000		277,000
Impairment of proved properties	172,641,000		208,923,000		219,037,000
Abandonment and impairment of unproved properties	46,105,000		16,342,000		7,367,000
Stock-based compensation expense	32,347,000		30,185,000		26,824,000
Change in Net Profits Plan liability	(21,842,000)		(28,904,000)		(25,477,000)
Derivative gain	(3,080,000)		(55,630,000)		(37,086,000)
Derivative cash settlement gain (loss)	22,062,000	[1]	44,264,000	[1]	(25,671,000)	[1]
Amortization of debt discount and deferred financing costs	5,390,000		6,769,000		18,299,000
Deferred income taxes	105,555,000		(29,638,000)		123,789,000
Plugging and abandonment	(9,946,000)		(2,856,000)		(5,849,000)
Other	2,775,000		527,000		(6,027,000)
Changes in current assets and liabilities:
Accounts receivable	(78,494,000)		(21,389,000)		(41,998,000)
Refundable income taxes	(1,266,000)		2,217,000		2,901,000
Prepaid expenses and other	1,364,000		(1,484,000)		16,376,000
Accounts payable and accrued expenses	93,224,000		31,136,000		(18,073,000)
Net cash provided by operating activities	1,338,514,000		921,969,000		760,532,000
Cash flows from investing activities:
Net proceeds from sale of oil and gas properties	424,849,000		55,375,000		364,522,000
Capital expenditures	(1,553,536,000)		(1,507,828,000)		(1,633,093,000)
Acquisition of proved and unproved oil and gas properties	(61,603,000)		(5,773,000)		0
Receipts from restricted cash related to 1031 exchange	(1,754,000)		0		0
Other	(859,000)		893,000		3,661,000
Net cash used in investing activities	(1,192,903,000)		(1,457,333,000)		(1,264,910,000)
Cash flows from financing activities:
Proceeds from credit facility	1,203,000,000		1,609,000,000		322,000,000
Repayment of credit facility	(1,543,000,000)		(1,269,000,000)		(370,000,000)
Debt issuance costs related to credit facility	(3,444,000)		0		(8,719,000)
Net proceeds from Senior Notes	490,185,000		392,138,000		684,242,000
Repayment of 3.50% Senior Convertible Notes	0		(287,500,000)		0
Proceeds from sale of common stock	6,858,000		5,816,000		7,327,000
Dividends paid	(6,663,000)		(6,511,000)		(6,382,000)
Net share settlement from issuance of stock awards	(16,220,000)		(21,622,000)		(9,973,000)
Other	(5,000)		(225,000)		0
Net cash provided by financing activities	130,711,000		422,096,000		618,495,000
Net change in cash and cash equivalents	276,322,000		(113,268,000)		114,117,000
Cash and cash equivalents at beginning of period	5,926,000		119,194,000		5,077,000
Cash and cash equivalents at end of period	282,248,000		5,926,000		119,194,000
Supplemental schedule of additional cash flow information and noncash investing and financing activities:
Cash paid for interest, net of capitalized interest	(70,702,000)		(51,328,000)		(22,133,000)
Net cash refunded for income taxes	204,000		1,389,000		4,046,000
Capital expenditures incurred but not yet paid	$ 217,820,000		$ 262,800,000		$ 214,800,000

[1] Total derivative cash settlement gain (loss) is reported in the derivative cash settlement gain (loss) line item on the consolidated statements of cash flows within net cash provided by operating activities.