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Inventories - Narrative (Details) - USD ($) $ in Millions | Sep. 30, 2018 | Jun. 30, 2018 | Dec. 31, 2017
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Inventory Disclosure [Abstract] |  |  |
Inventories valued on a LIFO basis | $ 1,339 |  | $ 1,208
Total inventories valued on an average-cost basis | $ 534 |  | $ 481
EP&S |  |  |
Segment Reporting Information [Line Items] |  |  |
Inventory adjustments |  | $ 23 |

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- Definition Amount of inventory reserves for last-in first-out (LIFO) and other inventory valuation methods. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 330 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=66092785&loc=d3e4492-108314 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.6(b)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition Amount by which inventory stated at last-in first-out (LIFO) is less than (in excess of) inventory stated at other inventory cost methods. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.6(c)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition The amount of LIFO (last in first out) inventory present at the reporting date when inventory is also valued using different valuation methods. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6361739&loc=d3e7789-107766 + Details
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