Investments (Details) - Additional Information - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Investments [Abstract]
Proceeds from sales of real estate investments	$ 31	$ 0	$ 0
Gains realized on sales of real estate investments	8
Accumulated depreciation on real estate held for investment purposes	497	462
Future minimum rental income expected on operating leases relating to the Company's real estate properties for 2022	117
Future minimum rental income expected on operating leases relating to the Company's real estate properties for 2023	93
Future minimum rental income expected on operating leases relating to the Company's real estate properties for 2024	75
Future minimum rental income expected on operating leases relating to the Company's real estate properties for 2025	51
Future minimum rental income expected on operating leases relating to the Company's real estate properties for 2026	36
Future minimum rental income expected on operating leases relating to the Company's real estate properties for 2027 and thereafter	$ 67
Combined average days to maturity of short-term securities (in days)	29 days
Amortized cost of short-term securities (which approximates fair value)	$ 3,836	$ 5,511
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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Combined average maturity (in days) on short-term securities.

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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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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 lease payment to be received by lessor for operating lease in next 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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