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Derivative Instruments (Total Fair Value Of Company's Derivative Assets And Liabilities By Instrument And Balance Sheet Location, Before Counterparty Netting) (Detail) - Not Designated as Hedging Instrument [Member] - Derivative Instrument [Member] - USD ($) $ in Millions | Mar. 31, 2021 | Dec. 31, 2020
--- | --- | ---
Derivative [Line Items] |  |  |
Derivative notional amount |  | $ 2,447 | $ 2,534
Derivative Assets, Not designated, Fair Value | [1] | 10 | 7
Derivative Liabilities, Not designated, Fair Value | [1] | (136) | (225)
Insured swaps [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative notional amount |  | 1,725 | 1,743
Insured swaps [Member] | Other assets [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative Assets, Not designated, Fair Value | [1] | 0 | 0
Insured swaps [Member] | Derivative liabilities [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative Liabilities, Not designated, Fair Value | [1] | (1) | (2)
Interest rate swaps [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative notional amount |  | 429 | 437
Interest rate swaps [Member] | Other assets [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative Assets, Not designated, Fair Value | [1] | 1 | 1
Interest rate swaps [Member] | Derivative liabilities [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative Liabilities, Not designated, Fair Value | [1] | (125) | (164)
Interest rate swaps-embedded [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative notional amount |  | 241 | 252
Interest rate swaps-embedded [Member] | Medium-term notes [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative Assets, Not designated, Fair Value | [1] | 0 | 0
Derivative Liabilities, Not designated, Fair Value | [1] | (10) | (10)
Currency swaps-VIE [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative notional amount |  | 52 | 53
Currency swaps-VIE [Member] | Other assets-VIE [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative Assets, Not designated, Fair Value | [1] | 9 | 6
Currency swaps-VIE [Member] | Derivative liabilities-VIE [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative Liabilities, Not designated, Fair Value | [1] | $ 0 | 0
All other [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative notional amount |  |  | 49
All other [Member] | Other assets [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative Assets, Not designated, Fair Value | [1] |  | 0
All other [Member] | Derivative liabilities [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative Liabilities, Not designated, Fair Value | [1] |  | $ (49)
[1] | In accordance with the accounting guidance for derivative instruments and hedging activities, the balance sheet location of the Company’s embedded derivative instruments is determined by the location of the related host contract.

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- Definition Fair value of derivative Asset Not Designated As Hedging Instrument, presented on a gross basis even when the derivative instrument is subject to master netting arrangements and qualifies for net presentation in the statement of financial position. + References No definition available. + Details
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- Definition Fair value of derivative liability Not Designated As Hedging Instrument, presented on a gross basis even when the derivative instrument is subject to master netting arrangements and qualifies for net presentation in the statement of financial position. + References No definition available. + 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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- Definition Nominal or face amount used to calculate payment on derivative. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1B -URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5580258-113959 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1A -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5579245-113959 + Details
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