CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating activities:
Net income	$ 634,382,000	$ 115,722,000	$ 13,002,000
Adjustments to reconcile net income to net cash provided from operating activities:
Loss (gain) from equity method investments, net of distributions	3,095,000	(2,973,000)	5,670,000
Deferred income tax expense	396,502,000	34,000,000	13,832,000
Depletion, depreciation and amortization and impairment	579,056,000	500,150,000	480,782,000
Exploration dry hole and impairment costs	16,145,000	5,699,000	841,000
Abandonment and impairment of unproved properties	47,079,000	51,918,000	125,278,000
Derivative fair value (income) loss	(383,520,000)	61,825,000	(41,437,000)
Cash settlements on derivative financial instruments that do not qualify for hedge accounting	(42,634,000)	(31,256,000)	38,700,000
Allowance for bad debt	250,000	250,000	750,000
Amortization of deferred financing costs, loss on extinguishment of debt and other	24,694,000	23,866,000	23,165,000
Deferred and stock-based compensation	(4,295,000)	119,398,000	60,136,000
Gain on the sale of assets	(285,638,000)	(92,291,000)	(49,132,000)
Changes in working capital:
Accounts receivable	(5,329,000)	(21,212,000)	(38,017,000)
Inventory and other	(4,521,000)	3,785,000	(7,376,000)
Accounts payable	(1,023,000)	(13,555,000)	13,654,000
Accrued liabilities and other	(20,108,000)	(11,788,000)	7,251,000
Net cash provided from operating activities	954,135,000	743,538,000	647,099,000
Investing activities:
Additions to natural gas and oil properties	(1,200,419,000)	(1,159,252,000)	(1,498,628,000)
Additions to field service assets	(11,863,000)	(5,925,000)	(4,762,000)
Acreage purchases	(211,971,000)	(132,145,000)	(191,065,000)
Equity method investments	1,103,000	3,799,000
Proceeds from disposal of assets	180,508,000	315,522,000	168,219,000
Purchases of marketable securities held by the deferred compensation plan	(30,898,000)	(36,136,000)	(60,406,000)
Proceeds from the sales of marketable securities held by the deferred compensation plan	28,084,000	30,701,000	58,084,000
Net cash used in investing activities	(1,245,456,000)	(983,436,000)	(1,528,558,000)
Financing activities:
Borrowings on credit facilities	2,107,000,000	1,684,000,000	1,773,000,000
Repayments on credit facilities	(1,884,000,000)	(1,923,000,000)	(1,221,000,000)
Issuance of subordinated notes		750,000,000	600,000,000
Repayment of subordinated notes	(312,000,000)	(259,063,000)	(259,375,000)
Dividends paid	(26,610,000)	(26,129,000)	(25,981,000)
Debt issuance costs	(8,866,000)	(12,448,000)	(12,605,000)
Issuance of common stock	396,562,000	343,000	2,073,000
Change in cash overdrafts	3,371,000	5,610,000	(1,126,000)
Proceeds from the sales of common stock held by the deferred compensation plan	15,964,000	20,681,000	26,633,000
Net cash provided from financing activities	291,421,000	239,994,000	881,619,000
Increase in cash and cash equivalents	100,000	96,000	160,000
Cash and cash equivalents at beginning of year	348,000	252,000	92,000
Cash and cash equivalents at end of year	$ 448,000	$ 348,000	$ 252,000