Number of Projects with Suspended Exploratory Well Costs (Detail)	12 Months Ended
Dec. 31, 2014 Project	Dec. 31, 2013 Project	Dec. 31, 2012 Project
Exploratory Wells Drilled [Line Items]
Number of projects with first capitalized well drilled in the preceding 12 months
Number of projects that have exploratory well costs capitalized for a period of greater than 12 months	1	1	1
Total projects	1	1	1

The number of projects for which exploratory well costs have been capitalized for a period of greater than one year after the completion of drilling.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 932

-SubTopic 235

-Section 50

-Paragraph 1B

-Subparagraph b

-URI http://asc.fasb.org/extlink&oid=8451039&loc=SL6806780-109447

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant