Investments - Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2025	Mar. 31, 2024
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized gains on securities	$ 3	$ 14
Net of tax
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized gains (losses) on securities before impairments	8	13
Impairment allowance on securities	(6)	(2)
Realized gains on securities	2	11
Change in unrealized	61	9
Total pretax
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized gains (losses) on securities before impairments	10	16
Impairment allowance on securities	(7)	(2)
Realized gains on securities	3	14
Change in unrealized	76	11
Fixed maturities
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized gains (losses) on securities before impairments	1	(4)
Impairment allowance on fixed maturity securities	(7)	(2)
Realized gains on securities	(6)	(6)
Change in unrealized	76	11
Equity securities
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized gains (losses) on securities before impairments	9	20
Realized gains on securities	9	20
Change in unrealized	0	0
Mortgage loans and other investments
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized gains (losses) on securities before impairments	0	0
Impairment allowance on mortgage loans and other investments	0	0
Realized gains on securities	0	0
Change in unrealized	0	0
Total tax effects
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized gains (losses) on securities before impairments	(2)	(3)
Impairment allowance on securities	1	0
Realized gains on securities	(1)	(3)
Change in unrealized	$ (15)	$ (2)

Change in unrealized appreciation depreciation.

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Increase (decrease) during the period in the allowance for credit losses on investments

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Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments.

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- Definition

Amount of realized gain (loss) on investment in debt and equity securities.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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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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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479106/326-30-50-9

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Amount of increase (decrease) in allowance for credit loss on financing receivable.

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Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef
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Amount of realized gain (loss) on investment in marketable security.

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