Commitments and Contingencies (Details) (USD $)	1 Months Ended	12 Months Ended							12 Months Ended					12 Months Ended				1 Months Ended
	Mar. 31, 2010	Dec. 31, 2012	Dec. 31, 2011	Nov. 30, 2011	Aug. 24, 2011	Jul. 12, 2011	Mar. 11, 2011	Dec. 31, 2012 SES and SEPCO [Member]	Dec. 31, 2012 SES [Member]	Nov. 30, 2012 SES [Member] MMcf	Mar. 31, 2012 SES [Member] mi MMcf	Dec. 31, 2012 Midstream Services and E&P [Member]	Dec. 31, 2012 Parent [Member]	Dec. 31, 2012 Exploration Program in Canada [Member]	Dec. 31, 2010 Exploration Program in Canada [Member] acre	Jun. 06, 2011 SEPCO [Member]	Feb. 28, 2009 SEPCO [Member] Sixth Amended Petition [Member]	Dec. 31, 2010 SEPCO [Member] Seventh Amended Petition [Member]	Nov. 30, 2010 SEPCO [Member] Seventh Amended Petition [Member]
Future Demand Transportation Charges Due 2013		$ 252,400,000
Future Demand Transportation Charges Due 2014		264,300,000
Future Demand Transportation Charges Due 2015		284,700,000
Future Demand Transportation Charges Due 2016		300,100,000
Future Demand Transportation Charges Due 2017		303,900,000
Future Demand Transportation Charges Due Thereafter (After 2017)		1,409,700,000
Aggregate annual lease payment for the 14 leased drilling rigs and equipment		19,400,000
Aggregate annual lease payment for the 11 leases for pressure pumping equipment for E&P		7,500,000
Operating Leases, Future Minimum Payments Due in 2013		75,500,000										30,500,000
Operating Leases, Future Minimum Payments, Due in 2014		66,000,000										17,400,000
Operating Leases, Future Minimum Payments, Due in 2015		41,400,000										10,500,000
Operating Leases, Future Minimum Payments, Due in 2016		32,100,000										8,900,000
Operating Leases, Future Minimum Payments, Due in 2017		16,800,000										3,400,000
Obligations for demand and similar charges under transportation agreements								2,800,000					100,000,000
Dekatherm per day of capacity									100,000
Operating Leases, Future Minimum Payments, Due Thereafter		31,100,000
SES transportation agreement, capacity per day in MMcf										130	150
Length of pipeline proposal, miles											121
Unrecorded capital investments obligation, Exploration program acres coverage (acres)															2,500,000.0
Unrecorded capital investments obligation															47,000,000
Unrecorded promissory note payable															44,500,000
Capital investments related to E&P program in Canada		11,600,000	18,700,000											25,800,000
Capital investment related to companys E&P segment related to Canada for December 31, 2012 and 2011		11,600,000	18,700,000											25,800,000
Litigation, Allegations		LitigationTovah EnergyIn February 2009, SEPCO was added as a defendant in a Third Amended Petition in the matter of Tovah Energy, LLC and Toby Berry-Helfand v. David Michael Grimes, et, al.  In the Sixth Amended Petition, filed in July 2010, in the 273rd District Court in Shelby County, Texas (collectively, the "Sixth Petition"), plaintiff alleged that, in 2005, they provided SEPCO with proprietary data regarding two prospects in the James Lime formation pursuant to a confidentiality agreement and that SEPCO refused to return the proprietary data to the plaintiff, subsequently acquired leases based upon such proprietary data and profited therefrom.  Among other things, the plaintiff's allegations in the Sixth Petition included various statutory and common law claims, including, but not limited to claims of misappropriation of trade secrets, violation of the Texas Theft Liability Act, breach of fiduciary duty and confidential relationships, various fraud based claims and breach of contract, including a claim of breach of a purported right of first refusal on all interests acquired by SEPCO between February 15, 2005 and February 15, 2006.  In the Sixth Petition, plaintiff sought actual damages of over $55.0 million as well as other remedies, including special damages and punitive damages of four times the amount of actual damages established at trial. Immediately before the commencement of the trial in November 2010, plaintiff was permitted, over SEPCO's objections, to file a Seventh Amended Petition claiming actual damages of $46.0 million and also seeking the equitable remedy of disgorgement of all profits for the misappropriation of trade secrets and the breach of fiduciary duty claims. In December 2010, the jury found in favor of the plaintiff with respect to all of the statutory and common law claims and awarded $11.4 million in compensatory damages. The jury did not, however, award the plaintiff any special, punitive or other damages. In addition, the jury separately determined that SEPCO's profits for purposes of disgorgement were $381.5 million. This profit determination does not constitute a judgment or an award. The plaintiff's entitlement to disgorgement of profits as an equitable remedy will be determined by the judge and it is within the judge's discretion to award none, some or all the amount of profit to the plaintiff.  On December 31, 2010, the plaintiff filed a motion to enter the judgment based on the jury's verdict.  On February 11, 2011, SEPCO filed a motion for a judgment notwithstanding the verdict and a motion to disregard certain findings.  On March 11, 2011, the plaintiff filed an amended motion for judgment and intervenor filed its motion for judgment seeking not only the monetary damages and the profits determined by the jury but also seeking, as a new remedy, a constructive trust for profits from 143 wells as well as future drilling and sales of properties in the prospect areas.  A hearing on the post-verdict motions was held on March 14, 2011.  At the suggestion of the judge, all parties voluntarily agreed to participate in non-binding mediation efforts.  The mediation occurred on April 6, 2011 and was unsuccessful. On June 6, 2011, SEPCO received by mail a letter dated June 2, 2011 from the judge, in which he made certain rulings with respect to the post-verdict motions and responses filed by the parties. In his rulings, the judge denied SEPCO's motion for judgment, judgment notwithstanding the verdict and to disregard certain findings. Plaintiff's and intervenor's claim for a constructive trust was denied but the judge ruled that plaintiff and intervenor shall recover from SEPCO $11.4 million and a reasonable attorney's fee of 40% of the total damages awarded and are entitled to recover on their claim for disgorgement.  The judge instructed that SEPCO calculate the profit on the designated wells for each respective period.  SEPCO performed the calculation and provided it to the judge in June 2011.  On July 5, 2011, plaintiff and intervenor filed a letter with the court raising objections to the accounting provided by SEPCO, to which SEPCO filed a response on July 11, 2011.  On July 12, 2011, the judge sent a letter to the parties in which he ruled that after reviewing the parties' respective position letters, he was awarding $23.9 million in disgorgement damages in favor of the plaintiff and intervenor.  In the July 12, 2011 letter, the judge instructed the plaintiff and intervenor to prepare a judgment for his approval prior to July 21, 2011 consistent with his findings in his June 2, 2011 letter and the disgorgement award.  On August 24, 2011, a judgment was entered pursuant to which plaintiff and intervenor are entitled to recover approximately $11.4 million in actual damages and approximately $23.9 million in disgorgement as well as prejudgment interest and attorneys' fees which currently are estimated to be up to $8.9 million and all costs of court of the plaintiff and intervenor. On September 23, 2011, SEPCO filed a motion for a new trial and on November 18, 2011 filed a notice of appeal. On November 30, 2011, the court approved SEPCO's supersedeas bond in the amount of $14.1 million, which stays execution on the judgment pending appeal. The bond covers the $11.4 million judgment for actual damages, plus $1.3 million in pre-judgment interest, $1.3 million in post-judgment interest (estimating two years for the duration of appeal), and court costs. On June 22, 2012, SEPCO filed its appellate brief and, on June 25, 2012, plaintiff and intervenor filed a cross-appellate brief seeking limited remand to reassess the disgorgement determination. The parties filed their responses to the appellate and cross-appellate briefs on or about November 7, 2012.  Both sides filed replies to the opposing party's responses in January 2013.  Oral arguments are expected to occur in spring 2013.  Based on the Company's understanding and judgment of the facts and merits of this case, including appellate defenses, and after considering the advice of counsel, the Company has determined that, although reasonably possible after exhaustion of all appeals, an adverse final outcome to this lawsuit is not probable.  As such, the Company has not accrued any amounts with respect to this lawsuit.  If the plaintiff and intervenor were to ultimately prevail in the appellate process, the Company currently estimates, based on the judgments to date, that SEPCO's potential liability would be up to $44.2 million, including interest and attorney's fees. The Company's assessment may change in the future due to occurrence of certain events, such as denied appeals, and such re-assessment could lead to the determination that the potential liability is probable and could be material to the Company's results of operations, financial position or cash flows.MunceyOn February 20, 2012, the Company became aware that SEPCO was named as a defendant in the matter of Gery Muncey v. Southwestern Energy Production Company, et al filed in the District Court of San Augustine County in Texas on January 31, 2012. The plaintiff in this case is also the intervenor in the Tovah Energy matter described above and alleged various claims including fraud, misappropriation and breach of fiduciary duty that are purportedly independent of the claims alleged in the Tovah Energy matter but arise from the substantially same circumstances involved in the Tovah Energy matter. SEPCO's motion for summary judgment was granted on July 9, 2012. On August 22, 2012, the court signed a final take-nothing judgment in SEPCO's favor. The deadlines for filing appeals have expired, so this matter has been resolved in SEPCO's favor.Bureau of Land ManagementIn March 2010, the Company's subsidiary, SEECO, was served with a subpoena from a federal grand jury in Little Rock, Arkansas.  Based on the documents requested under the subpoena and subsequent discussions described below, the Company believes the grand jury is investigating matters involving approximately 27 horizontal wells operated by SEECO in Arkansas, including whether appropriate leases or permits were obtained therefor and whether royalties and other production attributable to federal lands have been properly accounted for and paid.  The Company believes it has fully complied with all requests related to the federal subpoena and delivered its affidavit to that effect. The Company and representatives of the Bureau of Land Management and the U.S. Attorney have had discussions since the production of the documents pursuant to the subpoena.  In January 2011, the Company voluntarily produced additional materials informally requested by the government arising from these discussions.  Although, to the Company's knowledge, no proceeding in this matter has been initiated against SEECO, the Company cannot predict whether or when one might be initiated. The Company intends to fully comply with any further requests and to cooperate with any related investigation. No assurance can be made as to the time or resources that will need to be devoted to this inquiry or the impact of the final outcome of the discussions or any related proceeding. OtherWe are subject to various litigation, claims and proceedings that have arisen in the ordinary course of business. Management believes, individually or in aggregate, such litigation, claims and proceedings will not have a material adverse impact on our financial position, results of operations or cash flows but these matters are subject to inherent uncertainties and management's view may change in the future. If an unfavorable final outcome were to occur, there exists the possibility of a material impact on our financial position, results of operations or cash flows for the period in which the effect becomes reasonably estimable. We accrue for such items when a liability is both probable and the amount can be reasonably estimated.
Litigation, Monetary damages claimed by plaintiffs																	55,000,000		46,000,000
Litigation settlement, gross																		11,400,000
Number of wells for constructive trust profits							143
Litigation, portion of profits considered for disgorgement																11,400,000		381,500,000
Litigation, Interest and Attorney's Fees claimed by plaintiffs																40
Disgorgement damages awarded in favor of the plantiff and intervenor						23,900,000
Actual damages recoverable by plaintiff per August 24, 2011 judgement					11,400,000
Disgorgement recoverable by plaintiff per August 24, 2011 judgement					23,900,000
Prejudgement interest and attorney's fees recoverable by plaintiff per August 24, 2011 judgement					8,900,000
Value of SEPCO's supersedeas bond				14,100,000
Actual damages included in SEPCO's supersedeas bond				11,400,000
Pre-judgement interest covered by SEPCO's supersedeas bond				1,300,000
Post-judgement interest covered by SEPCO's supersedeas bond				1,300,000
Litigation, SEPCO's estimated gross liability including interest and attorney's fees.		$ 44,200,000
Number of horizontal wells operated by SEECO in Arkansas	27