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Acquisition (Details) - Alaska Segment [Member] - Operating Segments [Member] - USD ($) $ in Millions | 3 Months Ended |
--- | --- | ---
Jun. 30, 2018 | Jul. 31, 2018
Interest In WNS Assets and Alpine Pipeline [Member] |  |
Business Acquisition [Line Items] |  |
Costs Incurred, Acquisition of Oil and Gas Properties | $ 386 |
Percent Acquired | 22.00% |
Interest In Greater Kuparuk Area [Member] | Scenario Plan [Member] |  |
Business Acquisition [Line Items] |  |
Percent Acquired |  | 39.20%
Interest In Kuparuk Transportation Co [Member] | Scenario Plan [Member] |  |
Business Acquisition [Line Items] |  |
Percent Acquired |  | 38.00%

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- Definition Cost incurred, including capitalized costs and costs charged to expense, in acquisition of oil and gas properties. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 18 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=68064819&loc=d3e62014-109447 + Details
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- Details
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