Investments Investments (Schedule Of Amortized Cost and Fair Value of Available-for-sale Securities and Related OTTI Recognized in AOCI) (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	$ 87,873	$ 85,188
Debt Securities, Available-for-sale, Allowance for Credit Loss	(15)	(20)	$ (176)	$ 0
Available for Sale, Gross Unrealized Appreciation	3,801	5,655
Available for Sale, Gross Unrealized Depreciation	(588)	(124)
Available for sale, Fair Value	91,071	90,699
U.S. Treasury / Agency
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	2,413	2,471
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Available for Sale, Gross Unrealized Appreciation	121	199
Available for Sale, Gross Unrealized Depreciation	(7)	0
Available for sale, Fair Value	2,527	2,670
Non-U.S.
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	25,147	24,594
Debt Securities, Available-for-sale, Allowance for Credit Loss	(6)	(6)
Available for Sale, Gross Unrealized Appreciation	1,214	1,808
Available for Sale, Gross Unrealized Depreciation	(189)	(42)
Available for sale, Fair Value	26,166	26,354
Corporate and asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	35,224	34,095
Debt Securities, Available-for-sale, Allowance for Credit Loss	(9)	(14)
Available for Sale, Gross Unrealized Appreciation	1,474	2,322
Available for Sale, Gross Unrealized Depreciation	(289)	(72)
Available for sale, Fair Value	36,400	36,331
Mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	18,788	17,456
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Available for Sale, Gross Unrealized Appreciation	738	1,022
Available for Sale, Gross Unrealized Depreciation	(89)	(8)
Available for sale, Fair Value	19,437	18,470
Municipal
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	6,301	6,572
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Available for Sale, Gross Unrealized Appreciation	254	304
Available for Sale, Gross Unrealized Depreciation	(14)	(2)
Available for sale, Fair Value	$ 6,541	$ 6,874

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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