Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Cash flows from operating activities:
Net income	$ 108,735	$ 220,958
Adjustments to reconcile net income to net cash provided by operating activities:
Depletion, depreciation and amortization	230,763	181,418
Exploration expenses, including dry holes	7,954	27,163
Deferred income taxes	51,894	105,871
Gains (Losses) on Sales of Assets	(24,417)	(43,596)
Accretion of discount on asset retirement obligations	3,153	2,430
Discontinued operations	(158)	1,577
Amortization of Financing Costs and Discounts	4,844	9,870
Derivative related activity	95,884	(27,243)
Amortization of stock-based compensation	17,395	15,086
Amortization of deferred revenue	0	(10,459)
Other noncash items	(2,922)	(9,516)
Change in operating assets and liabilities, net of effects from acquisitions and dispositions:
Accounts receivable, net	(41,803)	(20,663)
Income taxes receivable	6,053	1,407
Inventories	825	(31,027)
Prepaid expenses	101	1,413
Other current assets	(636)	2,488
Accounts payable	(57,572)	19,326
Interest payable	(30,589)	(21,917)
Income taxes payable	84	16,941
Other current liabilities	(9,514)	(15,441)
Net cash provided by operating activities	360,074	426,086
Cash flows from investing activities:
Proceeds from disposition of assets, net of cash sold	46,184	58,514
Additions to oil and gas properties	(697,191)	(678,339)
Additions to other assets and other property and equipment, net	(56,169)	(59,841)
Net cash used in investing activities	(707,176)	(679,666)
Cash flows from financing activities:
Borrowings under long-term debt	304,922	134,000
Principal payments on long-term debt	(1,012,253)	(49,000)
Proceeds from Issuance of Common Stock	1,280,916	0
Distributions to noncontrolling interests	(8,885)	(8,957)
Payments of other liabilities	(210)	458
Exercise of long-term incentive plan stock options	1,047	1,008
Purchases of treasury stock	(19,202)	(56,129)
Excess tax benefits from share-based payment arrangements	1,688	12,938
Payment of financing fees	(2)	(1,261)
Dividends paid	(17)	(43)
Net cash provided by (used in) financing activities	548,004	33,014
Net increase (decrease) in cash and cash equivalents	200,902	(220,566)
Cash and cash equivalents, beginning of period	229,396	537,484
Cash and cash equivalents, end of period	$ 430,298	$ 316,918