Document And Entity Information (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2011	Mar. 02, 2012	Jun. 30, 2011
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	true
Document Period End Date	Dec. 31, 2011
Document Fiscal Year Focus	2011
Document Fiscal Period Focus	FY
Entity Registrant Name	ATP OIL & GAS CORP
Entity Central Index Key	0001123647
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		52,051,422
Entity Well-known Seasoned Issuer	No
Entity Public Float			$ 682.1
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Amendment Description	ATP Oil & Gas Corporation (the "Company") is filing this Amendment No. 1 on Form 10-K/A ("Amendment No. 1") solely to include XBRL (Extensible Business Reporting Language) information in Exhibit 101 that was excluded from our filed Annual Report on Form 10-K for the fiscal year ended December 31, 2011. This Amendment No. 1 makes no other changes to the Annual Report on Form 10-K as filed with the Securities and Exchange Commission on March 15, 2011. Exhibit 101 provides the following items formatted in eXtensible Business Reporting Language (XBRL): (i) Balance Sheets at December 31, 2011 and December 31, 2010; (ii) Statements of Operations for the fiscal years ended December 31, 2011, December 31, 2010 and December 31, 2009; (iii) Statements of Comprehensive Income (Loss) for the fiscal years ended December 31, 2011, December 31, 2010 and December 31, 2009; (iv) Statements of Cash Flows for the fiscal years ended December 31, 2011, December 31, 2010 and December 31, 2009; (v) Statements of Temporary Equity for the fiscal years ended December 31, 2011, December 31, 2010 and December 31, 2009; (vi) Statements of Shareholders' Equity for the fiscal years ended December 31, 2011, December 31, 2010 and December 31, 2009; (vii) Notes to Consolidated Financial Statements; (viii) Schedule I – Parent Company Financial Statements; and (ix) Schedule II – Valuation and Qualifying Accounts.

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