Organization	3 Months Ended
Mar. 31, 2012
Organization [Abstract]
Organization	Note 1 — Organization Organization ATP Oil & Gas Corporation is engaged internationally in the acquisition, development and production of oil and natural gas properties. Our management team has extensive engineering, geological, geophysical, technical and operational expertise in developing and operating properties in both our current and planned areas of operation. In the Gulf of Mexico and in the U.K. sector of the North Sea (the "North Sea"), we seek to acquire and develop properties with proved undeveloped reserves ("PUD") that are economically attractive to us but are not strategic to major or large independent exploration-oriented oil and gas companies. Occasionally we will acquire properties that are already producing or where previous drilling has encountered reservoirs that appear to contain commercially productive quantities of oil and gas even though the reservoirs do not meet the Security and Exchange Commission's definition of proved reserves. During 2011, we acquired three licenses in the Mediterranean Sea covering potential natural gas resources in the deepwater off the coast of Israel. In the Mediterranean Sea our licenses relate to exploratory prospects where drilling has occurred nearby and hydrocarbons have been discovered by others. In April 2012, we began drilling on the first of these exploratory licenses. Basis of Presentation The consolidated financial statements include our accounts, the accounts of our majority-owned limited partnership, ATP Infrastructure Partners, L.P. ("ATP-IP") and those of our wholly-owned subsidiaries; ATP Oil & Gas (UK) Limited, or "ATP (UK);" ATP Oil & Gas (Netherlands) B.V.; ATP Titan LLC, four wholly owned limited liability companies created to own our interests in ATP-IP and ATP Titan LLC and four other wholly owned limited liability companies formed related to our operations in the Mediterranean Sea. All intercompany transactions are eliminated in consolidation and we separate the redeemable noncontrolling interest in ATP-IP in the accompanying statements. The accompanying unaudited consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States ("GAAP") for interim financial information and reflect all adjustments (consisting of normal recurring adjustments) which are, in the opinion of management, necessary for a fair statement of the results of operations for the interim periods. The interim financial information and notes hereto should be read in conjunction with our 2011 Annual Report on Form 10-K. The results of operations for the three months ended March 31, 2012 are not necessarily indicative of results to be expected for the entire year. We have reclassified certain amounts applicable to prior periods to conform to current classifications. These reclassifications do not affect earnings.

Organization

3 Months Ended

Mar. 31, 2012

Note 1 — Organization

Organization

ATP Oil & Gas Corporation is engaged internationally in the acquisition, development and production of oil and natural gas properties. Our management team has extensive engineering, geological, geophysical, technical and operational expertise in developing and operating properties in both our current and planned areas of operation. In the Gulf of Mexico and in the U.K. sector of the North Sea (the "North Sea"), we seek to acquire and develop properties with proved undeveloped reserves ("PUD") that are economically attractive to us but are not strategic to major or large independent exploration-oriented oil and gas companies. Occasionally we will acquire properties that are already producing or where previous drilling has encountered reservoirs that appear to contain commercially productive quantities of oil and gas even though the reservoirs do not meet the Security and Exchange Commission's definition of proved reserves.

During 2011, we acquired three licenses in the Mediterranean Sea covering potential natural gas resources in the deepwater off the coast of Israel. In the Mediterranean Sea our licenses relate to exploratory prospects where drilling has occurred nearby and hydrocarbons have been discovered by others. In April 2012, we began drilling on the first of these exploratory licenses.

Basis of Presentation

The consolidated financial statements include our accounts, the accounts of our majority-owned limited partnership, ATP Infrastructure Partners, L.P. ("ATP-IP") and those of our wholly-owned subsidiaries; ATP Oil & Gas (UK) Limited, or "ATP (UK);" ATP Oil & Gas (Netherlands) B.V.; ATP Titan LLC, four wholly owned limited liability companies created to own our interests in ATP-IP and ATP Titan LLC and four other wholly owned limited liability companies formed related to our operations in the Mediterranean Sea. All intercompany transactions are eliminated in consolidation and we separate the redeemable noncontrolling interest in ATP-IP in the accompanying statements.

The accompanying unaudited consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States ("GAAP") for interim financial information and reflect all adjustments (consisting of normal recurring adjustments) which are, in the opinion of management, necessary for a fair statement of the results of operations for the interim periods. The interim financial information and notes hereto should be read in conjunction with our 2011 Annual Report on Form 10-K. The results of operations for the three months ended March 31, 2012 are not necessarily indicative of results to be expected for the entire year. We have reclassified certain amounts applicable to prior periods to conform to current classifications. These reclassifications do not affect earnings.