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, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	$ 77,835	$ 79,536
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	1,528	1,455
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	(424)	(876)
Available for sale, Fair Value	78,939	80,115
Available for sale, OTTI recognized in AOCI	(6)	(14)
US Treasury and Government [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	3,701	2,883
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	32	32
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	(35)	(45)
Available for sale, Fair Value	3,698	2,870
Available for sale, OTTI recognized in AOCI	0	0
Foreign Government Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	20,514	20,929
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	622	636
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	(106)	(125)
Available for sale, Fair Value	21,030	21,440
Available for sale, OTTI recognized in AOCI	(1)	(5)
Corporate securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	23,453	23,736
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	638	580
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	(95)	(167)
Available for sale, Fair Value	23,996	24,149
Available for sale, OTTI recognized in AOCI	(4)	(8)
Collateralized Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	15,279	14,066
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	111	135
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	(100)	(194)
Available for sale, Fair Value	15,290	14,007
Available for sale, OTTI recognized in AOCI	(1)	(1)
US States and Political Subdivisions Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	14,888	17,922
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	125	72
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	(88)	(345)
Available for sale, Fair Value	14,925	17,649
Available for sale, OTTI recognized in AOCI	$ 0	$ 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.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 9A
-URI http://asc.fasb.org/extlink&oid=82896770&loc=SL6284427-111562

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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-Section 50
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-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
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-Section 45
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Amount of debt securities categorized neither as held-to-maturity nor trading.

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