Organization And Summary Of Significant Accounting Policies (Narrative) (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Outstanding checks included in accounts payable	$ 17	$ 5
Natural gas and oil reserves discount	10.00%swn_NaturalGasAndOilReservesDiscount
Period of time needed to calculate ceiling value of reserves	12 months	12 months	12 months
Cash flow hedges impact on ceiling value, net of tax	4swn_CashFlowHedgesImpactOnCeilingValue
Net capitalized costs exceeding ceiling			$ 1,192swn_CapitalizedCostsExceedCeiling
Amount recognized is the largest amount of tax benefit, threshold	50.00%
Treasury stock, shares	11,055us-gaap_TreasuryStockShares	9,924us-gaap_TreasuryStockShares
NGL [Member]
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Full cost ceiling test, price	23.79	43.45
Henry Hub Natural Gas [Member]
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Full cost ceiling test, price	4.35	3.67	2.76
West Texas Intermediate Oil [Member]
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Full cost ceiling test, price	91.48	93.42	91.21
Stock Options [Member]
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Number of common shares, Issued upon assumed exercise of outstanding stock options	241,603	377,626
Outstanding options average exercise price	$ 34.03	$ 28.03
Antidilutive securities excluded from computation of earnings per share, shares	1,446,004	1,634,695	1,716,109
Restricted Stock [Member]
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Number of common shares, Issued upon assumed exercise of outstanding stock options	448,415	258,396
Antidilutive securities excluded from computation of earnings per share, shares	29,879	114,433	602,429
Performance Units [Member]
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Number of common shares, Effect of issuance of nonvested shares	273,918	0
Gathering Systems [Member]
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Straight-line depreciation period	25 years

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Capitalized Costs Exceed Ceiling

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Value of qualifying cash flow hedges used in calculating the ceiling limitation, which represents the best measure of estimated cash flows from future production of affected oil and gas reserves, as disclosed in the financial statement footnotes.

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Price used in the full cost ceiling test. Prior to the fourth quarter of 2009, this price was the quoted market price as of the balance sheet date (if the quoted price at the balance sheet date resulted in an impairment, management could previously use a more favorable quoted market price at a day subsequent to the balance sheet date but prior to the auditor's report on the affected financial statements). For all periods including and subsequent to the fourth quarter of 2009, this price is an average of the prices for the first-day-of-the-month during the previous 12 months.

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Natural Gas And Oil Reserves Discount

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Outstanding checks included as a component of accounts payable.

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Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of share based payment arrangements using the treasury stock method.

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Weighted average exercise price as of the balance sheet date for those equity-based payment arrangements exercisable and outstanding.

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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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