The expense recorded to reduce the value of oil and gas assets consisting of proved properties and unproved properties as the estimate of future successful production from these properties is reduced.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=64862545&loc=d3e2921-110230

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 932
-SubTopic 360
-Section 35
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=66906256&loc=d3e66150-109466

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3602-108585

Name:	us-gaap_ImpairmentOfOilAndGasProperties
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Subsequent Events (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended
Subsequent Events (Details) - USD ($) $ in Millions	Apr. 30, 2016	Mar. 31, 2016	Mar. 31, 2015
Subsequent Event [Line Items]
Impairment of Oil and Gas Properties		$ 1	$ 0
Minimum [Member] \| Gulf of Mexico Assets [Member] \| Subsequent Event [Member]
Subsequent Event [Line Items]
Impairment of Oil and Gas Properties	$ 140
Maximum [Member] \| Gulf of Mexico Assets [Member] \| Subsequent Event [Member]
Subsequent Event [Line Items]
Impairment of Oil and Gas Properties	$ 150