Investments (Fair Value And Gross Unrealized Losses In A Continuous Unrealized Loss Position) (Details) $ in Millions	Dec. 31, 2017 USD ($) security	Dec. 31, 2016 USD ($) security
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value
Less Than or Equal to Twelve Months	$ 5,844	$ 17,813
Greater Than Twelve Months	6,063	4,155
Fair Value - Total	11,907	21,968
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Losses and OTTI
Less Than or Equal to Twelve Months	89	659
Greater Than Twelve Months	374	507
Losses - Total	$ 463	$ 1,166
Total number of AFS securities in an unrealized loss position | security	1,128	1,744
Equity AFS securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value
Less Than or Equal to Twelve Months	$ 22	$ 4
Greater Than Twelve Months	8	44
Fair Value - Total	30	48
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Losses and OTTI
Less Than or Equal to Twelve Months	14	2
Greater Than Twelve Months	3	2
Losses - Total	17	4
Fixed maturity AFS securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value
Less Than or Equal to Twelve Months	5,822	17,809
Greater Than Twelve Months	6,055	4,111
Fair Value - Total	11,877	21,920
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Losses and OTTI
Less Than or Equal to Twelve Months	75	657
Greater Than Twelve Months	371	505
Losses - Total	446	1,162
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	4,854	15,820
Greater Than Twelve Months	4,893	3,187
Fair Value - Total	9,747	19,007
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Losses and OTTI
Less Than or Equal to Twelve Months	68	569
Greater Than Twelve Months	288	403
Losses - Total	356	972
ABS [Member] | Fixed maturity AFS securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value
Less Than or Equal to Twelve Months	62	201
Greater Than Twelve Months	151	298
Fair Value - Total	213	499
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Losses and OTTI
Less Than or Equal to Twelve Months	1	4
Greater Than Twelve Months	15	25
Losses - Total	16	29
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	156	18
Greater Than Twelve Months	19
Fair Value - Total	175	18
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	1
Losses - Total	1	2
Foreign 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		29
Fair Value - Total		29
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Losses and OTTI
Less Than or Equal to Twelve Months		1
Losses - Total		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	302	989
Greater Than Twelve Months	641	392
Fair Value - Total	943	1,381
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Losses and OTTI
Less Than or Equal to Twelve Months	4	58
Greater Than Twelve Months	36	23
Losses - Total	40	81
CMBS [Member] | Fixed maturity AFS securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value
Less Than or Equal to Twelve Months	113	190
Greater Than Twelve Months	60	19
Fair Value - Total	173	209
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Losses and OTTI
Less Than or Equal to Twelve Months		4
Greater Than Twelve Months	3	2
Losses - Total	3	6
CLOs [Member] | Fixed maturity AFS securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value
Less Than or Equal to Twelve Months	281	259
Greater Than Twelve Months	72	25
Fair Value - Total	353	284
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Losses and OTTI
Less Than or Equal to Twelve Months	2	3
Losses - Total	2	3
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	34	227
Greater Than Twelve Months	93	47
Fair Value - Total	127	274
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Losses and OTTI
Less Than or Equal to Twelve Months		12
Greater Than Twelve Months	6	8
Losses - Total	6	20
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	20	76
Greater Than Twelve Months	126	143
Fair Value - Total	146	219
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Losses and OTTI
Less Than or Equal to Twelve Months		4
Greater Than Twelve Months	22	44
Losses - Total	$ 22	$ 48