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, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 614	$ 582	$ 623	$ 537
Total gains (losses) recognized in net income	(1)	8	(4)	(231)
Total gains (losses) recognized in accumulated other comprehensive loss	0	(3)	2	(2)
Purchases	44	54	86	329
Sales	(9)	(12)	(31)	(16)
Settlements	(21)	(23)	(43)	(31)
Transfers into Level III	0	42	3	63
Transfers out of Level III	(11)	(1)	(20)	(2)
Ending balance	616	647	616	647
Change in unrealized losses included in net income related to assets still held	2	7	0	38
Corporate Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	297	260	287	229
Total gains (losses) recognized in net income	(3)	1	(4)	1
Total gains (losses) recognized in accumulated other comprehensive loss	0	(3)	2	(2)
Purchases	30	42	63	62
Sales	(1)	(11)	(2)	(15)
Settlements	(19)	(23)	(40)	(30)
Transfers into Level III	0	38	0	59
Transfers out of Level III	(7)	0	(9)	0
Ending balance	297	304	297	304
Change in unrealized 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	6	5	6	5
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	(1)	0	(1)	0
Transfers into Level III	0	0	0	0
Transfers out of Level III	(2)	0	(2)	0
Ending balance	3	5	3	5
Change in unrealized 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	14	14	17	16
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	9	2	9
Sales	0	0	0	0
Settlements	(1)	0	(2)	(1)
Transfers into Level III	0	4	3	4
Transfers out of Level III	(2)	(1)	(9)	(2)
Ending balance	11	26	11	26
Change in unrealized 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	297	303	313	287
Total gains (losses) recognized in net income	2	7	0	(232)
Total gains (losses) recognized in accumulated other comprehensive loss	0	0	0	0
Purchases	14	3	21	258
Sales	(8)	(1)	(29)	(1)
Settlements	0	0	0	0
Transfers into Level III	0	0	0	0
Transfers out of Level III	0	0	0	0
Ending balance	305	312	305	312
Change in unrealized losses included in net income related to assets still held	$ 2	$ 7	$ 0	$ 38