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Investments (Real Estate and Real Estate Joint Ventures) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Real Estate [Line Items]
Leased real estate investments, Carrying Value	$ 5,245		$ 5,245		$ 5,450
Other real estate investments, Carrying Value	440		440		419
Real estate joint ventures, Carrying Value	6,216		6,216		6,064
Real Estate Investments, Net	11,901		11,901		$ 11,933
Income (Loss) from Equity Method Investments	1,000	$ (688)	2,300	$ (365)
Real Estate and Real Estate Joint Ventures
Real Estate [Line Items]
Gross Investment Income, Operating	205	102	381	267
Leased real estate investments
Real Estate [Line Items]
Operating Lease, Lease Income	108	101	219	207
Other real estate investments
Real Estate [Line Items]
Operating Lease, Lease Income	44	24	86	59
Real estate joint ventures
Real Estate [Line Items]
Income (Loss) from Equity Method Investments	$ 53	$ (23)	$ 76	$ 1