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Derivative Financial Instruments - Additional Information (Detail) - USD ($) | 6 Months Ended |
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Jun. 30, 2018 | Dec. 31, 2017
Derivative [Line Items] |  |
Notional value | $ 6,500,000,000 |
Net derivatives | 30,000,000 | $ 20,000,000
Cash collateral held relative to derivative exposure | 0 | 0
Cash collateral pledged | 28,000,000 | $ 22,000,000
Chicago Mercantile Exchange |  |
Derivative [Line Items] |  |
Notional value | $ 5,900,000,000 |
Percent of total notional derivative contracts | 90.30% |
London Clearing House |  |
Derivative [Line Items] |  |
Notional value | $ 600,000,000 |
Percent of total notional derivative contracts | 9.70% |

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- Definition Aggregate notional amount specified by the derivative(s). Expressed as an absolute value. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 12 -Section 13 -Sentence Column B + Details
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- Definition Derivative, Cash Collateral Held Relative to Derivative Exposure, Net + References No definition available. + Details
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- Definition Derivative Instrument, Percent of Total Notional Derivative Contracts + References No definition available. + Details
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- Definition Fair values as of the balance sheet date of the net amount of all assets and liabilities resulting from contracts that meet the criteria of being accounted for as derivative instruments. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -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 + Details
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- Definition Amount of right to receive cash collateral under master netting arrangements that have not been offset against derivative liabilities. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226016-175313 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 8 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=109980867&loc=d3e41678-113959 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (d)(2) -URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312 + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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- Details
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- Details
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