Investments (Details) - Additional Information - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Investments [Abstract]
Proceeds from sales of real estate investments	$ 64	$ 0	$ 10
Gains realized on sales of real estate investments	17		4
Realized losses included in net realized investment losses related to real estate impairments	5	9	$ 12
Accumulated depreciation on real estate held for investment purposes	581	556
Future minimum rental income expected on operating leases relating to the Company's real estate properties for 2025	118
Future minimum rental income expected on operating leases relating to the Company's real estate properties for 2026	107
Future minimum rental income expected on operating leases relating to the Company's real estate properties for 2027	93
Future minimum rental income expected on operating leases relating to the Company's real estate properties for 2028	72
Future minimum rental income expected on operating leases relating to the Company's real estate properties for 2029	46
Future minimum rental income expected on operating leases relating to the Company's real estate properties for 2030 and thereafter	$ 87
Combined average days to maturity of short-term securities (in days)	23 days
Amortized cost of short-term securities (which approximates fair value)	$ 4,766	$ 5,137
Availability of financial information provided by hedge funds following the date of the reporting	1 month
Availability of financial information provided by private equity and real estate partnerships following the date of the reporting, maximum	3 months
Minimum percentage of equity interest that must be held by the Company in order for the investment in a VIE to be considered significant	20.00%

Number of months within which financial information provided by hedge funds is available following the reporting date.

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Maximum number of months before which financial information provided by private equity and real estate partnerships is available following the reporting date.

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The minimum percentage of equity interest that must be held by the Company in order for the investment in a VIE to be considered significant.

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The net gain (loss) resulting from sales and other disposals of real estate owned for investment purposes.

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The charge against earnings in the period to reduce the carrying amount of real property to fair value.

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Amount of lease payment to be received by lessor for operating lease in fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of short-term investments classified as other.

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Cash received from the sale of real estate that is held for investment, that is, it is part of an investing activity during the period.

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The cumulative amount of depreciation for real estate property held for investment purposes.

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