Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
Statement of Cash Flows [Abstract]
Cash and cash equivalents	$ 1,321	$ 12,413
Operating Activities
Net Income (Loss)	502,614	120,461
Income from discontinued operations	(469,490)	(24,213)
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion and amortization	399,568	332,247
Asset impairment	179,074	0
Accretion of discount on asset retirement obligations	5,650	5,187
Deferred income taxes	287,855	58,665
Change in derivative fair value	(53,928)	53,581
(Gain) loss on sale of assets	105	(91)
Stock-based compensation expense	10,837	11,200
Exploration, including dry holes	10,808	8,759
Discontinued operations	112,180	149,462
Other, net	(1,972)	10,013
Net change in:
Accounts receivable	(28,486)	31,051
Inventories	(3,243)	7,836
Accounts payable	27,967	(58,003)
Income taxes	(266,229)	16,061
Pension and other postretirement benefit contributions	(2,397)	(5,484)
Other current assets and liabilities	(1,625)	11,284
Net cash provided by operating activities	709,288	728,016
Investing Activities
Additions to oil and natural gas properties	(906,166)	(894,713)
Acquisitions, net of cash acquired	(26,371)	(21,400)
Proceeds from sale of Alabama Gas Corporation and other assets	1,347,904	2,382
Purchase of short-term investments	(377,000)	0
Sale of short-term investments	359,000	0
Discontinued operations	(51,850)	(54,052)
Other, net	0	(405)
Net cash provided by (used in) investing activities	345,517	(968,188)
Financing Activities
Payment of dividends on common stock	(32,840)	(31,454)
Issuance of common stock	23,053	13,680
Reduction of long-term debt	(600,000)	0
Payment of debt issuance costs	(7,912)	0
Net change in credit facility	(410,100)	286,000
Tax benefit on stock compensation	3,873	2,710
Discontinued operations	(35,113)	(28,055)
Net cash provided by (used in) financing activities	(1,059,039)	242,881
Net increase (decrease) in cash and cash equivalents	(4,234)	2,709
Cash and cash equivalents at beginning of period	$ 5,555	$ 9,704