Divestitures - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	0 Months Ended	1 Months Ended
Jan. 16, 2014 Cut Off and Clovelly Fields [Member]	Jan. 31, 2014 Hatch Point Field [Member]
Business Acquisition [Line Items]
Sale of interest cash consideration	$ 44.8	$ 9.7
Estimates asset retirement obligations	9.2	1.2
Gain or loss recognized from the sale of interest		$ 0

Amount of gain (loss) on sale or disposal of equity in securities of subsidiaries.

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 13

-Subparagraph g

-Article 9

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration