Investments - Unrealized Loss (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	$ 25,806	$ 27,288
Gross Unrealized Losses	2,767	3,039
Additional impairment losses	0
AAA
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	1,423	1,800
Gross Unrealized Losses	265	282
AA
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	3,971	4,247
Gross Unrealized Losses	701	730
A
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	6,254	6,330
Gross Unrealized Losses	527	582
BBB
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	10,922	11,548
Gross Unrealized Losses	849	980
U.S. Government, Government agencies and Government-sponsored enterprises
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	2,212	2,567
Gross Unrealized Losses	322	373
Non-investment grade
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	1,024	796
Gross Unrealized Losses	$ 103	$ 92

Amount of additional other-than-temporary impairment losses on investments in available-for-sale securities.

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in unrealized loss position without allowance for credit loss.

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Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in unrealized loss position, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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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.

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