Investments - Schedule of Unrealized Loss (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	$ 31,117	$ 29,511
Gross Unrealized Losses	4,888	4,056
Additional impairment losses	0
AAA
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	1,893	1,559
Gross Unrealized Losses	382	298
AA
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	4,458	4,327
Gross Unrealized Losses	1,037	817
A
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	7,240	6,615
Gross Unrealized Losses	913	749
BBB
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	13,704	13,226
Gross Unrealized Losses	1,881	1,621
U.S. Government, Government agencies and Government-sponsored enterprises
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	2,620	2,355
Gross Unrealized Losses	466	337
Non-investment grade
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	1,202	1,429
Gross Unrealized Losses	$ 209	$ 234

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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