Investments Investments (Schedule Of Amortized Cost and Fair Value of Available-for-sale Securities and Related OTTI Recognized in AOCI) (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Available for sale, at amortized cost	$ 80,363	$ 79,536
Available-for-sale,Gross Unrealized Gain	1,693	1,455
Available-for-sale, Gross Unrealized Depreciation	(411)	(876)
Available for sale, Fair Value	81,645	80,115
Available for sale, OTTI recognized in AOCI	(10)	(14)
US Treasury and Government [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for sale, at amortized cost	3,122	2,883
Available-for-sale,Gross Unrealized Gain	40	32
Available-for-sale, Gross Unrealized Depreciation	(26)	(45)
Available for sale, Fair Value	3,136	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, at amortized cost	21,139	20,929
Available-for-sale,Gross Unrealized Gain	653	636
Available-for-sale, Gross Unrealized Depreciation	(82)	(125)
Available for sale, Fair Value	21,710	21,440
Available for sale, OTTI recognized in AOCI	(2)	(5)
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for sale, at amortized cost	24,744	23,736
Available-for-sale,Gross Unrealized Gain	714	580
Available-for-sale, Gross Unrealized Depreciation	(94)	(167)
Available for sale, Fair Value	25,364	24,149
Available for sale, OTTI recognized in AOCI	(7)	(8)
Collateralized Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for sale, at amortized cost	14,469	14,066
Available-for-sale,Gross Unrealized Gain	148	135
Available-for-sale, Gross Unrealized Depreciation	(144)	(194)
Available for sale, Fair Value	14,473	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, at amortized cost	16,889	17,922
Available-for-sale,Gross Unrealized Gain	138	72
Available-for-sale, Gross Unrealized Depreciation	(65)	(345)
Available for sale, Fair Value	16,962	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 50
-Paragraph 2
-Subparagraph (aaa)
-URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27161-111563

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
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-Section 45
-Paragraph 14A
-URI http://asc.fasb.org/extlink&oid=66004124&loc=SL7669686-108580

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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt securities classified as available-for-sale.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Amount of debt securities categorized neither as held-to-maturity nor trading.

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