Gains and Losses Included in Net Income (Loss) from Assets Measured at Fair Value (Detail) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2023	Mar. 31, 2022
Fair value of financial instruments [Abstract]
Total realized and unrealized gains (losses) included in net income, assets	$ 2	$ (4)
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest
Total gains (losses) included in net income attributable to assets still held, assets	$ 1	$ (1)
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest
Net Investment Income
Fair value of financial instruments [Abstract]
Total realized and unrealized gains (losses) included in net income, assets	$ 3	$ 2
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest
Total gains (losses) included in net income attributable to assets still held, assets	$ 2	$ 2
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest
Net investment gains (losses)
Fair value of financial instruments [Abstract]
Total realized and unrealized gains (losses) included in net income, assets	$ (1)	$ (6)
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest
Total gains (losses) included in net income attributable to assets still held, assets	$ (1)	$ (3)
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest

Indicates line item in statement in which net income is reported that includes unrealized gain (loss) from asset measured at fair value using unobservable input (level 3) and still held.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (d)
-URI https://asc.fasb.org/extlink&oid=126976982&loc=d3e19207-110258

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- Definition

Amount of unrealized gain (loss) recognized in income from asset measured at fair value on recurring basis using unobservable input (level 3) and still held.

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- References

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- Definition

Amount of gain (loss) recognized in income from asset measured at fair value on recurring basis using unobservable input (level 3).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)
-URI https://asc.fasb.org/extlink&oid=126976982&loc=d3e19207-110258

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- Definition

Indicates line item in statement in which net income is reported that includes gain (loss) from asset measured at fair value using unobservable input (level 3).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)
-URI https://asc.fasb.org/extlink&oid=126976982&loc=d3e19207-110258

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