Investments (Fair Value And Gross Unrealized Losses In A Continuous Unrealized Loss Position) (Details) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 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	$ 16,142	$ 17,813
Greater Than Twelve Months	3,651	4,155
Continuous Unrealized Loss Position, Total	19,793	21,968
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Losses and OTTI
Less Than or Equal to Twelve Months	553	659
Greater Than Twelve Months	385	507
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	$ 938	$ 1,166
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | security	1,584	1,744
Equity AFS securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value
Less Than or Equal to Twelve Months	$ 13	$ 4
Greater Than Twelve Months	40	44
Continuous Unrealized Loss Position, Total	53	48
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Losses and OTTI
Less Than or Equal to Twelve Months	2	2
Greater Than Twelve Months	1	2
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	3	4
Fixed maturity securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value
Less Than or Equal to Twelve Months	16,129	17,809
Greater Than Twelve Months	3,611	4,111
Continuous Unrealized Loss Position, Total	19,740	21,920
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Losses and OTTI
Less Than or Equal to Twelve Months	551	657
Greater Than Twelve Months	384	505
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	935	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	14,068	15,820
Greater Than Twelve Months	2,790	3,187
Continuous Unrealized Loss Position, Total	16,858	19,007
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Losses and OTTI
Less Than or Equal to Twelve Months	471	569
Greater Than Twelve Months	302	403
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	773	972
ABS [Member] | Fixed maturity securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value
Less Than or Equal to Twelve Months	121	201
Greater Than Twelve Months	270	298
Continuous Unrealized Loss Position, Total	391	499
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Losses and OTTI
Less Than or Equal to Twelve Months	4	4
Greater Than Twelve Months	22	25
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	26	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	170	18
Continuous Unrealized Loss Position, Total	170	18
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Losses and OTTI
Less Than or Equal to Twelve Months	2	2
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	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
Continuous Unrealized Loss Position, Total		29
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Losses and OTTI
Less Than or Equal to Twelve Months		1
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses		1
RMBS [Member] | Fixed maturity securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value
Less Than or Equal to Twelve Months	996	989
Greater Than Twelve Months	325	392
Continuous Unrealized Loss Position, Total	1,321	1,381
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Losses and OTTI
Less Than or Equal to Twelve Months	52	58
Greater Than Twelve Months	15	23
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	67	81
CMBS [Member] | Fixed maturity securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value
Less Than or Equal to Twelve Months	210	190
Greater Than Twelve Months	18	19
Continuous Unrealized Loss Position, Total	228	209
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Losses and OTTI
Less Than or Equal to Twelve Months	4	4
Greater Than Twelve Months	2	2
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	6	6
CLOs [Member] | Fixed maturity securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value
Less Than or Equal to Twelve Months	277	259
Greater Than Twelve Months	21	25
Continuous Unrealized Loss Position, Total	298	284
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Losses and OTTI
Less Than or Equal to Twelve Months	3	3
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	3	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	231	227
Greater Than Twelve Months	46	47
Continuous Unrealized Loss Position, Total	277	274
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Losses and OTTI
Less Than or Equal to Twelve Months	12	12
Greater Than Twelve Months	6	8
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	18	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	56	76
Greater Than Twelve Months	141	143
Continuous Unrealized Loss Position, Total	197	219
Available-for-sale Securities, Continuous Unrealized Loss Position, Gross Unrealized Losses and OTTI
Less Than or Equal to Twelve Months	3	4
Greater Than Twelve Months	37	44
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	$ 40	$ 48