Investments (Fair Value And Gross Unrealized Losses In A Continuous Unrealized Loss Position) (Details) $ in Millions	Sep. 30, 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	$ 9,089	$ 17,813
Greater Than Twelve Months	2,760	4,155
Fair Value - Total	11,849	21,968
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Losses and OTTI
Less Than or Equal to Twelve Months	258	659
Greater Than Twelve Months	274	507
Losses - Total	$ 532	$ 1,166
Total number of AFS securities in an unrealized loss position | security	1,052	1,744
Equity AFS securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value
Less Than or Equal to Twelve Months	$ 26	$ 4
Greater Than Twelve Months	8	44
Fair Value - Total	34	48
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Losses and OTTI
Less Than or Equal to Twelve Months	11	2
Greater Than Twelve Months	2	2
Losses - Total	13	4
Fixed maturity securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value
Less Than or Equal to Twelve Months	9,063	17,809
Greater Than Twelve Months	2,752	4,111
Fair Value - Total	11,815	21,920
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Losses and OTTI
Less Than or Equal to Twelve Months	247	657
Greater Than Twelve Months	272	505
Losses - Total	519	1,162
Corporate bonds [Member] | Fixed maturity securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value
Less Than or Equal to Twelve Months	7,624	15,820
Greater Than Twelve Months	2,273	3,187
Fair Value - Total	9,897	19,007
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Losses and OTTI
Less Than or Equal to Twelve Months	206	569
Greater Than Twelve Months	218	403
Losses - Total	424	972
ABS [Member] | Fixed maturity securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value
Less Than or Equal to Twelve Months	88	201
Greater Than Twelve Months	156	298
Fair Value - Total	244	499
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Losses and OTTI
Less Than or Equal to Twelve Months	2	4
Greater Than Twelve Months	17	25
Losses - Total	19	29
U.S. government bonds [Member] | Fixed maturity securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value
Less Than or Equal to Twelve Months	172	18
Fair Value - Total	172	18
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Losses and OTTI
Less Than or Equal to Twelve Months	2	2
Losses - Total	2	2
Foreign government bonds [Member] | Fixed maturity 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 securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value
Less Than or Equal to Twelve Months	770	989
Greater Than Twelve Months	128	392
Fair Value - Total	898	1,381
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Losses and OTTI
Less Than or Equal to Twelve Months	31	58
Greater Than Twelve Months	8	23
Losses - Total	39	81
CMBS [Member] | Fixed maturity securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value
Less Than or Equal to Twelve Months	126	190
Greater Than Twelve Months	7	19
Fair Value - Total	133	209
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Losses and OTTI
Less Than or Equal to Twelve Months	2	4
Greater Than Twelve Months	1	2
Losses - Total	3	6
CLOs [Member] | Fixed maturity securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value
Less Than or Equal to Twelve Months	175	259
Greater Than Twelve Months	6	25
Fair Value - Total	181	284
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Losses and OTTI
Less Than or Equal to Twelve Months	1	3
Losses - Total	1	3
State and municipal bonds [Member] | Fixed maturity securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value
Less Than or Equal to Twelve Months	88	227
Greater Than Twelve Months	57	47
Fair Value - Total	145	274
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Losses and OTTI
Less Than or Equal to Twelve Months	3	12
Greater Than Twelve Months	5	8
Losses - Total	8	20
Hybrid and redeemable preferred securities [Member] | Fixed maturity 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	125	143
Fair Value - Total	145	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	23	44
Losses - Total	$ 23	$ 48