Investments (Components of Net Investment Gains Losses) (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Other net investment gains (losses):
Mortgage loans	$ 60	$ (63)
Real estate and real estate joint ventures	48	1
Other limited partnership interests	(5)	4
Other (2)	20	24
Subtotal - investment portfolio gains (losses)	134	(313)
Change In Estimated Fair Value Of Other Limited Partnership Interests And Real Estate Joint Ventures	9	1
Non-investment portfolio gains (losses)	(9)	24
Subtotal	0	25
Total net investment gains (losses)	134	(288)
Changes In Estimated Fair Value Subsequent To Purchase For Equity Securities	71	(288)
Fixed Maturity Securities
Marketable Securities, Gain (Loss) [Abstract]
Net investment gains (losses)	(67)	4
Equity Securities
Marketable Securities, Gain (Loss) [Abstract]
Net investment gains (losses)	75	(284)
Cash Flow Hedging [Member]
Other net investment gains (losses):
Total net investment gains (losses)	21	8
Currency Swap [Member] \| Cash Flow Hedging [Member]
Other net investment gains (losses):
Total net investment gains (losses)	(219)	(451)
FVO Securities (1)
Marketable Securities, Gain (Loss) [Abstract]
Net investment gains (losses)	3	1
Foreign Currency Gain (Loss) [Member] \| Reclassification out of Accumulated Other Comprehensive Income \| Currency Swap [Member] \| Cash Flow Hedging [Member]
Other net investment gains (losses):
Total net investment gains (losses)	$ 29	$ 12

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