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Fair Value Measurements - Assets and Liabilities Accounted for at Fair Value on Recurring Basis (Detail) - USD ($) $ in Millions | Mar. 31, 2018 | Dec. 31, 2017
--- | --- | ---
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |  |
Cash collateral netted with derivative liabilities |  | $ 39 |  | $ 8
Embedded derivatives in commodity contracts |  |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |  |
Embedded derivatives, current |  | 11 |  | 12
Fair Value, Measurements, Recurring |  |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |  |
Commodity derivative instruments, assets - netting and collateral |  | (21) |  | (118)
Commodity derivative instruments, assets - collateral pledged not offset |  | 22 |  | 8
Other assets |  | 3 |  | 3
Total assets at fair value |  | 3 |  | 12
Commodity derivative instruments, liabilities - netting and collateral |  | (60) |  | (126)
Commodity derivative instruments, liabilities - collateral pledged not offset |  | 0 |  | 0
Total liabilities at fair value |  | 60 |  | 66
Fair Value, Measurements, Recurring | Commodity derivatives |  |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |  |
Commodity derivative instruments, assets - netting and collateral | [1] | (21) |  | (118)
Commodity derivative instruments, assets - net carrying value on balance sheet | [2] | 0 |  | 9
Commodity derivative instruments, assets - collateral pledged not offset |  | 22 |  | 8
Commodity derivative instruments, liabilities - netting and collateral | [1] | (60) |  | (126)
Commodity derivative instruments, liabilities - net carrying value on balance sheet | [2] | 1 |  | 2
Commodity derivative instruments, liabilities - collateral pledged not offset |  | 0 |  | 0
Fair Value, Measurements, Recurring | Embedded derivatives in commodity contracts |  |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |  |
Commodity derivative instruments, liabilities - netting and collateral |  | 0 |  | 0
Commodity derivative instruments, liabilities - net carrying value on balance sheet | [2] | 59 |  | 64
Commodity derivative instruments, liabilities - collateral pledged not offset |  | 0 |  | 0
Fair Value, Measurements, Recurring | Level 1 |  |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |  |
Other assets |  | 3 |  | 3
Total assets at fair value |  | 24 |  | 130
Total liabilities at fair value |  | 60 |  | 126
Fair Value, Measurements, Recurring | Level 1 | Commodity derivatives |  |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |  |
Commodity derivative instruments, assets - gross |  | 21 |  | 127
Commodity derivative instruments, liabilities - gross |  | 60 |  | 126
Fair Value, Measurements, Recurring | Level 1 | Embedded derivatives in commodity contracts |  |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |  |
Commodity derivative instruments, liabilities - gross |  | 0 |  | 0
Fair Value, Measurements, Recurring | Level 2 |  |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |  |
Other assets |  | 0 |  | 0
Total assets at fair value |  | 0 |  | 0
Total liabilities at fair value |  | 0 |  | 0
Fair Value, Measurements, Recurring | Level 2 | Commodity derivatives |  |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |  |
Commodity derivative instruments, assets - gross |  | 0 |  | 0
Commodity derivative instruments, liabilities - gross |  | 0 |  | 0
Fair Value, Measurements, Recurring | Level 2 | Embedded derivatives in commodity contracts |  |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |  |
Commodity derivative instruments, liabilities - gross |  | 0 |  | 0
Fair Value, Measurements, Recurring | Level 3 |  |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |  |
Other assets |  | 0 |  | 0
Total assets at fair value |  | 0 |  | 0
Total liabilities at fair value |  | 60 |  | 66
Fair Value, Measurements, Recurring | Level 3 | Commodity derivatives |  |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |  |
Commodity derivative instruments, assets - gross |  | 0 |  | 0
Commodity derivative instruments, liabilities - gross |  | 1 | [3] | 2
Fair Value, Measurements, Recurring | Level 3 | Embedded derivatives in commodity contracts |  |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |  |
Commodity derivative instruments, liabilities - gross | [3] | $ 59 |  | $ 64
[1] | Represents the impact of netting assets, liabilities and cash collateral when a legal right of offset exists. As of March 31, 2018, cash collateral of $39 million was netted with the mark-to-market derivative liabilities. As of December 31, 2017, $8 million was netted with mark-to-market derivative liabilities.
[2] | We have no derivative contracts that are subject to master netting arrangements reflected gross on the balance sheet.
[3] | Level 3 includes $11 million and $12 million classified as current at March 31, 2018 and December 31, 2017, respectively.

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- Definition Fair value of liability associated with financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, and obligation to return cash collateral under master netting arrangements. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 45 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41228-113958 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=82849420&loc=SL20226003-175313 + Details
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