Investments Investments (Schedule Of Amortized Cost and Fair Value of Available-for-sale Securities and Related OTTI Recognized in AOCI) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	$ 85,188	$ 82,580
Debt Securities, Available-for-sale, Allowance for Credit Loss	20	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	5,655	3,074
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(124)	(166)
Available for sale, Fair Value	90,699	85,488
Available for sale, OTTI recognized in AOCI		(30)
US Treasury and Government [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	2,471	3,188
Debt Securities, Available-for-sale, Allowance for Credit Loss	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	199	96
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	0	(1)
Available for sale, Fair Value	2,670	3,283
Available for sale, OTTI recognized in AOCI		0
Foreign
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	24,594	22,670
Debt Securities, Available-for-sale, Allowance for Credit Loss	(6)
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1,808	1,099
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(42)	(62)
Available for sale, Fair Value	26,354	23,707
Available for sale, OTTI recognized in AOCI		(25)
Corporate securities
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	34,095	30,689
Debt Securities, Available-for-sale, Allowance for Credit Loss	(14)
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	2,322	1,180
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(72)	(78)
Available for sale, Fair Value	36,331	31,791
Available for sale, OTTI recognized in AOCI		(5)
Collateralized Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	17,456	18,712
Debt Securities, Available-for-sale, Allowance for Credit Loss	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1,022	494
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(8)	(14)
Available for sale, Fair Value	18,470	19,192
Available for sale, OTTI recognized in AOCI		0
States, municipalities, and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	6,572	7,321
Debt Securities, Available-for-sale, Allowance for Credit Loss	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	304	205
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(2)	(11)
Available for sale, Fair Value	$ 6,874	7,515
Available for sale, OTTI recognized in AOCI		$ 0

Accumulated other comprehensive loss related to portion of other than temporary impairment (OTTI) due to factors other than credit losses on debt securities categorized as available-for-sale that an entity does not intend to sell and which it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis of the debt security. The amount represented by this item is net of tax, as applicable.

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