Fair Value Measurements - Gains or Losses Recorded Related to Fair Value Option (Details) - Fair Value Option - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2024	Mar. 31, 2023
Fair Value, Option, Quantitative Disclosures
Fair value option gain (loss)	$ 209	$ 212
Other bond securities
Fair Value, Option, Quantitative Disclosures
Fair value option gain (loss)	78	136
Alternative investments
Fair Value, Option, Quantitative Disclosures
Fair value option gain (loss)	130	77
Long-term debt
Fair Value, Option, Quantitative Disclosures
Fair value option gain (loss)	$ 1	$ (1)

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.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 30
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482907/825-10-50-30

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 31
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482907/825-10-50-31

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482907/825-10-50-32

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