Investments (Fair Value And Gross Unrealized Losses In A Continuous Unrealized Loss Position) (Details) $ in Millions	Mar. 31, 2018 USD ($) security	Dec. 31, 2017 USD ($) security
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value
Less Than or Equal to Twelve Months	$ 22,188	$ 5,844
Greater Than Twelve Months	5,672	6,063
Fair Value - Total	27,860	11,907
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Losses and OTTI
Less Than or Equal to Twelve Months	549	89
Greater Than Twelve Months	524	374
Losses - Total	$ 1,073	$ 463
Total number of AFS securities in an unrealized loss position \| security	2,208	1,128
Equity Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value
Less Than or Equal to Twelve Months		$ 22
Greater Than Twelve Months		8
Fair Value - Total		30
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Losses and OTTI
Less Than or Equal to Twelve Months		14
Greater Than Twelve Months		3
Losses - Total		17
Fixed maturity AFS securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value
Less Than or Equal to Twelve Months		5,822
Greater Than Twelve Months		6,055
Fair Value - Total		11,877
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Losses and OTTI
Less Than or Equal to Twelve Months		75
Greater Than Twelve Months		371
Losses - Total		446
Corporate Bonds [Member] \| Fixed maturity AFS securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value
Less Than or Equal to Twelve Months	$ 20,141	4,854
Greater Than Twelve Months	4,547	4,893
Fair Value - Total	24,688	9,747
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Losses and OTTI
Less Than or Equal to Twelve Months	510	68
Greater Than Twelve Months	424	288
Losses - Total	934	356
ABS [Member] \| Fixed maturity AFS securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value
Less Than or Equal to Twelve Months	107	62
Greater Than Twelve Months	141	151
Fair Value - Total	248	213
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Losses and OTTI
Less Than or Equal to Twelve Months	2	1
Greater Than Twelve Months	14	15
Losses - Total	16	16
U.S. government bonds [Member] \| Fixed maturity AFS securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value
Less Than or Equal to Twelve Months	100	156
Greater Than Twelve Months	18	19
Fair Value - Total	118	175
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Losses and OTTI
Less Than or Equal to Twelve Months	1
Greater Than Twelve Months	2	1
Losses - Total	3	1
RMBS [Member] \| Fixed maturity AFS securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value
Less Than or Equal to Twelve Months	700	302
Greater Than Twelve Months	608	641
Fair Value - Total	1,308	943
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Losses and OTTI
Less Than or Equal to Twelve Months	20	4
Greater Than Twelve Months	53	36
Losses - Total	73	40
CMBS [Member] \| Fixed maturity AFS securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value
Less Than or Equal to Twelve Months	450	113
Greater Than Twelve Months	59	60
Fair Value - Total	509	173
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Losses and OTTI
Less Than or Equal to Twelve Months	10
Greater Than Twelve Months	4	3
Losses - Total	14	3
CLOs [Member] \| Fixed maturity AFS securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value
Less Than or Equal to Twelve Months	547	281
Greater Than Twelve Months	75	72
Fair Value - Total	622	353
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Losses and OTTI
Less Than or Equal to Twelve Months	3	2
Losses - Total	3	2
State and municipal bonds [Member] \| Fixed maturity AFS securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value
Less Than or Equal to Twelve Months	107	34
Greater Than Twelve Months	100	93
Fair Value - Total	207	127
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Losses and OTTI
Less Than or Equal to Twelve Months	2
Greater Than Twelve Months	8	6
Losses - Total	10	6
Hybrid and redeemable preferred securities [Member] \| Fixed maturity AFS securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value
Less Than or Equal to Twelve Months	36	20
Greater Than Twelve Months	124	126
Fair Value - Total	160	146
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Losses and OTTI
Less Than or Equal to Twelve Months	1
Greater Than Twelve Months	19	22
Losses - Total	$ 20	$ 22

Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale that have been in a continuous loss position for twelve months or longer.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 6
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27290-111563

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