CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Dec. 31, 2014
CONDENSED CONSOLIDATED BALANCE SHEETS [Abstract]
Natural gas and oil properties, using the full cost method, costs excluded from amortization	$ 4,997	$ 4,646
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	1,250,000,000us-gaap_CommonStockSharesAuthorized	1,250,000,000us-gaap_CommonStockSharesAuthorized
Common stock, shares issued	384,572,080us-gaap_CommonStockSharesIssued	354,488,992us-gaap_CommonStockSharesIssued
Preferred stock, par value	$ 0.01
Preferred stock, shares authorized	10,000,000us-gaap_PreferredStockSharesAuthorized
Preferred stock, dividend rate	6.25%
Preferred stock, liquidation preference per share	$ 1,000
Preferred stock, shares issued	1,725,000us-gaap_PreferredStockSharesIssued
Preferred stock, shares outstanding	1,725,000us-gaap_PreferredStockSharesOutstanding
Treasury stock, shares	13,893us-gaap_TreasuryStockShares	11,055us-gaap_TreasuryStockShares

The sum of the capitalized costs incurred, as of the balance sheet date, of unproved properties excluded from amortization including acquisition costs, exploration costs, development costs, and production costs.

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Face amount or stated value per share of common stock.

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The maximum number of common shares permitted to be issued by an entity's charter and bylaws.

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Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury.

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The percentage rate used to calculate dividend payments on preferred stock.

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The per share liquidation preference (or restrictions) of nonredeemable preferred stock (or preferred stock redeemable solely at the option of the issuer) that has a preference in involuntary liquidation considerably in excess of the par or stated value of the shares. The liquidation preference is the difference between the preference in liquidation and the par or stated values of the share.

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Face amount or stated value per share of preferred stock nonredeemable or redeemable solely at the option of the issuer.

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The maximum number of nonredeemable preferred shares (or preferred stock redeemable solely at the option of the issuer) permitted to be issued by an entity's charter and bylaws.

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Total number of nonredeemable preferred shares (or preferred stock redeemable solely at the option of the issuer) issued to shareholders (includes related preferred shares that were issued, repurchased, and remain in the treasury). May be all or portion of the number of preferred shares authorized. Excludes preferred shares that are classified as debt.

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Aggregate share number for all nonredeemable preferred stock (or preferred stock redeemable solely at the option of the issuer) held by stockholders. Does not include preferred shares that have been repurchased.

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Number of common and preferred shares that were previously issued and that were repurchased by the issuing entity and held in treasury on the financial statement date. This stock has no voting rights and receives no dividends.

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