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, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	$ 79,536	$ 43,149
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	1,455	1,168
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	(876)	(730)
Available for sale, Fair Value	80,115	43,587
Available for sale, OTTI recognized in AOCI	(14)	(42)
US Treasury and Government [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	2,883	2,481
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	32	52
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	(45)	(5)
Available for sale, Fair Value	2,870	2,528
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	20,929	13,190
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	636	468
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	(125)	(213)
Available for sale, Fair Value	21,440	13,445
Available for sale, OTTI recognized in AOCI	(5)	(13)
Corporate securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	23,736	15,028
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	580	355
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	(167)	(454)
Available for sale, Fair Value	24,149	14,929
Available for sale, OTTI recognized in AOCI	(8)	(28)
Collateralized Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	14,066	9,827
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	135	183
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	(194)	(52)
Available for sale, Fair Value	14,007	9,958
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	17,922	2,623
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	72	110
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	(345)	(6)
Available for sale, Fair Value	17,649	2,727
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
-SubTopic 10
-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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