Asset Acquisitions, Dispositions and Other (Details) - USD ($) $ in Billions	1 Months Ended
Apr. 30, 2017	Jun. 30, 2017
Non-strategic acreage in Andrews and Martin Counties, Texas \| Held for sale
Asset Acquisitions, Dispositions and Other
Sale consideration		$ 0.6
South Texas operations \| Disposed of by sale
Asset Acquisitions, Dispositions and Other
Sale consideration	$ 0.5
Pre-tax gain on disposal	$ 0.5
Permian EOR
Asset Acquisitions, Dispositions and Other
Cost of acquired business assets		$ 0.6

Amount before tax of gain (loss) not previously recognized resulting from the disposal of a discontinued operation.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 45
-Paragraph 3B
-URI http://asc.fasb.org/extlink&oid=65878427&loc=SL51721525-107759

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=64827811&loc=d3e1361-107760

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=65878427&loc=d3e957-107759

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