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Investments (Real Estate and Real Estate Joint Ventures) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Real Estate [Line Items]
Leased real estate investments, Carrying Value	$ 1,587		$ 1,587		$ 1,586
Other real estate investments, Carrying Value	408		408		419
Real estate joint ventures, Carrying Value	5,026		5,026		4,654
Real estate and real estate joint ventures (includes $1,404 and $1,378, respectively, relating to variable interest entities and $147 and $127, respectively, under the fair value option)	7,021		7,021		$ 6,659
Income (Loss) from Equity Method Investments	301	$ 144	17	$ 337
Leased real estate investments
Real Estate [Line Items]
Operating Lease, Lease Income	47	40	140	121
Other real estate investments
Real Estate [Line Items]
Operating Lease, Lease Income	37	46	86	126
Real estate joint ventures
Real Estate [Line Items]
Income (Loss) from Equity Method Investments	(43)	18	(63)	36
Real estate and real estate joint ventures
Real Estate [Line Items]
Gross Investment Income, Operating	$ 41	$ 104	$ 163	$ 283