Investments (Rollforward of expected credit-losses, AFS) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]
Debt Securities, Available for sale, Allowance for Credit Loss	$ 122	$ 193	$ 122	$ 193	$ 115	$ 156	$ 168	$ 169
Debt Securities, Available-for-sale, Allowance for Credit Loss, Period Increase (Decrease)	41	79	72	138
Debt Securities, Available-for-sale, Allowance for Credit Loss, Writeoff	0	(2)	(5)	(4)
Debt Securities, Available-for-sale, Allowance for Credit Loss, Recovery	$ (34)	$ (52)	$ (101)	$ (110)

Amount of allowance for credit loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Amount of increase (decrease) in allowance for credit loss of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
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Amount of increase in allowance for credit loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), from recovery.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Amount of writeoff of allowance for credit loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

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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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