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Fair Value Measurements (Schedule Of Significant Unobservable Inputs Used In Level 3 Liability Valuations) (Detail) - USD ($) $ in Millions | 3 Months Ended |  |  |
--- | --- | --- | --- | ---
Mar. 31, 2021 | Dec. 31, 2020 | Mar. 31, 2020 | [3] | Dec. 31, 2019 | [3]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |  |  |  |  |  |
Fair Value Measurements, Valuation Processes, Description |  | Actuarial model |  |  |  |  |
Weighted Average [Member] |  |  |  |  |  |  |
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |  |  |  |  |  |
Long-Duration Contracts, Assumptions by Product and Guarantee, Lapse Rate | [1] | 4.60% |  |  |  |  |
Significant Unobservable Inputs Annuitization Rate | [1] | 3.40% |  |  |  |  |
Minimum [Member] |  |  |  |  |  |  |
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |  |  |  |  |  |
Long-Duration Contracts, Assumptions by Product and Guarantee, Lapse Rate |  | 3.00% |  |  |  |  |
Significant Unobservable Inputs Annuitization Rate |  | 0.00% |  |  |  |  |
Maximum [Member] |  |  |  |  |  |  |
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |  |  |  |  |  |
Long-Duration Contracts, Assumptions by Product and Guarantee, Lapse Rate |  | 34.00% |  |  |  |  |
Significant Unobservable Inputs Annuitization Rate |  | 100.00% |  |  |  |  |
Level 3 | GLB |  |  |  |  |  |  |
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |  |  |  |  |  |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability Value |  | $ 760 | [2] | $ 1,089 | [2] | $ 1,591 | $ 897
Level 3 | Fair Value, Recurring [Member] | GLB |  |  |  |  |  |  |
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |  |  |  |  |  |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability Value |  |  |  | $ 1,089 |  |  |
[1] | The weighted average lapse and annuitization rates are determined by weighting each treaty's rates by the GLB contracts fair value.
[2] | Our GLB reinsurance product meets the definition of a derivative instrument for accounting purposes and is accordingly carried at fair value.
[3] | Our GLB reinsurance product meets the definition of a derivative instrument for accounting purposes and is accordingly carried at fair value.

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- Definition Fair value of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258 + Details
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- Definition Description of the valuation processes in place for fair value measurements categorized within Level 3 of the fair value hierarchy. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f) -URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258 + Details
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