Subsequent Events (Sale & Purch) (Details) (USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended	12 Months Ended		1 Months Ended
Jan. 31, 2013	May 31, 2012	Dec. 31, 2012	Mar. 31, 2013 [ProductionPaymentTransactionMember]	Mar. 31, 2013 [ProductionPaymentTransactionMember] [AlbaBacchusFieldsMember] [EndeavourEnergyUnitedKingdomMember]
Subsequent Event [Line Items]
Subsequent Event Month			March 2013		March 2013
Subsequent Event, Description			In January 2013, we entered into the Procurement Agreement with an unaffiliated third party entity, which matures on July 9, 2014. The Procurement Agreement was entered into in connection with the unaffiliated third party’s entry into a credit support arrangement with a providing bank. Pursuant to this credit support arrangement, the third party pledged cash, contributed by one of our shareholders, to secure letters of credit in the amount of $33.0 million. The letters of credit secure decommissioning obligations in connection with certain of our U.K. license agreements.		In March 2013, our wholly-owned subsidiary, EEUK, entered into a sale and purchase agreement (the “Sale and Purchase Agreement”) for $107.5 million providing for the sale and purchase of a production payment over the proceeds of sale from a proportion of EEUK’s entitlement to production from its interests in the Alba and Bacchus fields located in the UK sector of the North Sea (the “Production Payment Transaction”) and the issuance of warrants (discussed below). Repayment of the production payment will come solely from the proceeds from the sale of production from EEUK’s entitlement from the Alba and Bacchus fields. In the event that the Production Payment Transaction is not consummated under the terms of the Sale and Purchase Agreement, the deposit paid to EEUK upon signing of the Sale and Purchase Agreement and all or part of a $1.2 million termination fee would become due and payable by EEUK. The completion of the Production Payment Transaction is conditional upon, amongst other things, the approval of the UK Secretary of State for Energy and Climate Change. Contemporaneously with completion under the Sale and Purchase Agreement, we expect to issue 3,440,000 warrants to purchase shares of common stock at an exercise price of $3.014 per share (the “Warrants”). EEUK’s obligations to refund the deposit and pay the termination fee are secured by first priority liens on EEUK’s interests in the licenses and certain joint operating agreements governing the fields giving rise to the production subject to the production payment. Upon closing of the purchase and sale of the production payment, EEUK’s obligations under the production payment will be secured by first priority liens in the same assets and second priority liens in certain other assets of the Company and its subsidiaries.
Monetary Production Payment				$ 107.5
Sale And Purchase Agreement Termination Fee					$ 1.2
Shares Issued For Investment Warrants	1,000,000	2,000,000			3,440,000
Investment Warrants, Exercise Price	$ 7.31	$ 10.50			$ 3.014

In January 2013, we entered into the Procurement Agreement with an unaffiliated third party entity, which matures on July 9, 2014. The Procurement Agreement was entered into in connection with the unaffiliated third party’s entry into a credit support arrangement with a providing bank. Pursuant to this credit support arrangement, the third party pledged cash, contributed by one of our shareholders, to secure letters of credit in the amount of $33.0 million. The letters of credit secure decommissioning obligations in connection with certain of our U.K. license agreements.

In March 2013, our wholly-owned subsidiary, EEUK, entered into a sale and purchase agreement (the “Sale and Purchase Agreement”) for $107.5 million providing for the sale and purchase of a production payment over the proceeds of sale from a proportion of EEUK’s entitlement to production from its interests in the Alba and Bacchus fields located in the UK sector of the North Sea (the “Production Payment Transaction”) and the issuance of warrants (discussed below). Repayment of the production payment will come solely from the proceeds from the sale of production from EEUK’s entitlement from the Alba and Bacchus fields. In the event that the Production Payment Transaction is not consummated under the terms of the Sale and Purchase Agreement, the deposit paid to EEUK upon signing of the Sale and Purchase Agreement and all or part of a $1.2 million termination fee would become due and payable by EEUK. The completion of the Production Payment Transaction is conditional upon, amongst other things, the approval of the UK Secretary of State for Energy and Climate Change. Contemporaneously with completion under the Sale and Purchase Agreement, we expect to issue 3,440,000 warrants to purchase shares of common stock at an exercise price of $3.014 per share (the “Warrants”). EEUK’s obligations to refund the deposit and pay the termination fee are secured by first priority liens on EEUK’s interests in the licenses and certain joint operating agreements governing the fields giving rise to the production subject to the production payment. Upon closing of the purchase and sale of the production payment, EEUK’s obligations under the production payment will be secured by first priority liens in the same assets and second priority liens in certain other assets of the Company and its subsidiaries.

Sale And Purchase Agreement Termination Fee

$ 1.2

Investment Warrants, Exercise Price

$ 7.31

$ 10.50

$ 3.014