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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) - Derivative Instrument [Member] - Not Designated as Hedging Instrument [Member] - USD ($) $ in Millions | Jun. 30, 2019 | Dec. 31, 2018
--- | --- | ---
Derivative [Line Items] |  |  |
Derivative notional amount |  | $ 3,024 | $ 3,619
Derivative Assets, Not designated, Fair Value | [1] | 13 | 18
Derivative Liabilities, Not designated, Fair Value | [1] | (253) | (212)
Interest Rate Swaps [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative notional amount |  | 681 | 712
Credit Default Swap [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative notional amount |  | 52 | 70
Insured Swaps [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative notional amount |  | 1,947 | 2,433
Interest Rate Swaps Embedded [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative notional amount |  | 235 | 293
Currency swaps-VIE [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative notional amount |  | 60 | 62
All Other [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative notional amount |  | 49 | 49
Derivative Liabilities [Member] | Interest Rate Swaps [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative Liabilities, Not designated, Fair Value | [1] | (199) | (157)
Derivative Liabilities [Member] | Credit Default Swap [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative Liabilities, Not designated, Fair Value | [1] | (18) | (33)
Derivative Liabilities [Member] | Insured Swaps [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative Liabilities, Not designated, Fair Value | [1] | (2) | (2)
Derivative Liabilities [Member] | All Other [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative Liabilities, Not designated, Fair Value | [1] | (16) | (7)
Medium-term Notes [Member] | Interest Rate Swaps Embedded [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative Assets, Not designated, Fair Value | [1] | 0 |
Derivative Liabilities, Not designated, Fair Value | [1] | (18) | (13)
Other Assets [Member] | Interest Rate Swaps [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative Assets, Not designated, Fair Value | [1] | 2 | 2
Other Assets [Member] | Credit Default Swap [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative Assets, Not designated, Fair Value | [1] | 0 |
Other Assets [Member] | Insured Swaps [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative Assets, Not designated, Fair Value | [1] | 0 |
Other Assets [Member] | All Other [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative Assets, Not designated, Fair Value | [1] | 0 |
Other Assets V I E [Member] | Currency swaps-VIE [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative Assets, Not designated, Fair Value | [1] | 11 | $ 16
Derivative Liabilities V I E [Member] | Currency swaps-VIE [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative Liabilities, Not designated, Fair Value | [1] | $ 0 |
[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 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 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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