Amount of cash paid to acquire the entity.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141R

-Paragraph 68

-Subparagraph f(1)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141

-Paragraph 51

-Subparagraph d

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Name:	us-gaap_BusinessAcquisitionCostOfAcquiredEntityCashPaid
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Acquisitions - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	Jun. 18, 2012	Jun. 18, 2012 Block Deep Water Pompano Field Mississippi Canyon	Jun. 18, 2012 Mississippi Canyon Block 29	Jun. 18, 2012 Mississippi Canyon Block 72	Dec. 28, 2011 Bp Exploration and Production Inc	Dec. 28, 2011 Adjacent Mississippi Canyon Block 29	Dec. 28, 2011 Mica Field	Dec. 28, 2011 Pompano Field
Business Acquisition [Line Items]
Percentage of working interest acquired		25.00%	14.00%	10.00%
Cash consideration transferred	$ 26.4
Percentage of operated working capital acquired					75.00%	51.00%
Percentage of non-operated working capital acquired							50.00%	75.00%