Fair Value (Reconciliation Of The Beginning And Ending Balances Of Assets Measured At Fair Value On A Recurring Basis Using Level III Inputs) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 405	$ 614	$ 397	$ 623
Total gains (losses) recognized in net income	(9)	(1)	(17)	(4)
Total gains (losses) recognized in accumulated other comprehensive loss	(7)	0	(17)	2
Purchases	17	44	54	86
Sales	(14)	(9)	(26)	(31)
Settlements	(9)	(21)	(21)	(43)
Transfers into Level III	0	0	13	3
Transfers out of Level III	0	(11)	0	(20)
Ending balance	383	616	383	616
Change in unrealized gains (losses) included in net income related to assets still held	(10)	(2)	(17)	0
Corporate Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	316	297	303	287
Total gains (losses) recognized in net income	1	(3)	(1)	(4)
Total gains (losses) recognized in accumulated other comprehensive loss	(7)	0	(17)	2
Purchases	14	30	39	63
Sales	(1)	(1)	(4)	(2)
Settlements	(9)	(19)	(19)	(40)
Transfers into Level III	0	0	13	0
Transfers out of Level III	0	(7)	0	(9)
Ending balance	314	297	314	297
Change in unrealized gains (losses) included in net income related to assets still held	0	0	0	0
Residential Mortgage-Backed Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	2	6	2	6
Total gains (losses) recognized in net income	0	0	0	0
Total gains (losses) recognized in accumulated other comprehensive loss	0	0	0	0
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements	0	(1)	0	(1)
Transfers into Level III	0	0	0	0
Transfers out of Level III	0	(2)	0	(2)
Ending balance	2	3	2	3
Change in unrealized gains (losses) included in net income related to assets still held	0	0	0	0
Other Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	5	14	7	17
Total gains (losses) recognized in net income	0	0	0	0
Total gains (losses) recognized in accumulated other comprehensive loss	0	0	0	0
Purchases	0	0	0	2
Sales	0	0	0	0
Settlements	0	(1)	(2)	(2)
Transfers into Level III	0	0	0	3
Transfers out of Level III	0	(2)	0	(9)
Ending balance	5	11	5	11
Change in unrealized gains (losses) included in net income related to assets still held	0	0	0	0
Equity Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	82	297	85	313
Total gains (losses) recognized in net income	(10)	2	(16)	0
Total gains (losses) recognized in accumulated other comprehensive loss	0	0	0	0
Purchases	3	14	15	21
Sales	(13)	(8)	(22)	(29)
Settlements	0	0	0	0
Transfers into Level III	0	0	0	0
Transfers out of Level III	0	0	0	0
Ending balance	62	305	62	305
Change in unrealized gains (losses) included in net income related to assets still held	$ (10)	$ (2)	$ (17)	$ 0