Loans And Allowance For Credit Losses (Summary Of Information On Impaired Loans) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	$ 272	$ 238
Impaired Financing Receivable, Recorded Investment	229	261
Impaired Financing Receivable, Related Allowance	10	8
Impaired Financing Receivable, Interest Income, Accrual Method	5	9
Impaired Financing Receivable, Unpaid Principal Balance	269	310
Commercial And Industrial [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	103	83
Impaired Financing Receivable, Recorded Investment	104	88
Impaired Financing Receivable, Related Allowance	7	4
Impaired Financing Receivable, Interest Income, Accrual Method	2	0
Impaired Financing Receivable, Unpaid Principal Balance	132	112
Owner Occupied [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	61	47
Impaired Financing Receivable, Recorded Investment	51	60
Impaired Financing Receivable, Related Allowance	1	2
Impaired Financing Receivable, Interest Income, Accrual Method	1	8
Impaired Financing Receivable, Unpaid Principal Balance	53	67
Municipal [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	0	1
Impaired Financing Receivable, Recorded Investment	0	1
Impaired Financing Receivable, Related Allowance	0	0
Impaired Financing Receivable, Interest Income, Accrual Method	0	0
Impaired Financing Receivable, Unpaid Principal Balance	0	1
Commercial Portfolio Segment [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	164	131
Impaired Financing Receivable, Recorded Investment	155	149
Impaired Financing Receivable, Related Allowance	8	6
Impaired Financing Receivable, Interest Income, Accrual Method	3	8
Impaired Financing Receivable, Unpaid Principal Balance	185	180
Term [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	34	41
Impaired Financing Receivable, Recorded Investment	17	40
Impaired Financing Receivable, Related Allowance	0	0
Impaired Financing Receivable, Interest Income, Accrual Method	0	1
Impaired Financing Receivable, Unpaid Principal Balance	18	44
Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	34	42
Impaired Financing Receivable, Recorded Investment	17	40
Impaired Financing Receivable, Related Allowance	0	0
Impaired Financing Receivable, Interest Income, Accrual Method	0	1
Impaired Financing Receivable, Unpaid Principal Balance	18	45
Home Equity Line of Credit [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	15	13
Impaired Financing Receivable, Recorded Investment	13	14
Impaired Financing Receivable, Related Allowance	0	0
Impaired Financing Receivable, Interest Income, Accrual Method	1	0
Impaired Financing Receivable, Unpaid Principal Balance	14	15
One Through Four Family Residential [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	56	51
Impaired Financing Receivable, Recorded Investment	44	57
Impaired Financing Receivable, Related Allowance	2	2
Impaired Financing Receivable, Interest Income, Accrual Method	1	0
Impaired Financing Receivable, Unpaid Principal Balance	52	69
Construction And Other Consumer Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	2	1
Impaired Financing Receivable, Recorded Investment	0	1
Impaired Financing Receivable, Related Allowance	0	0
Impaired Financing Receivable, Interest Income, Accrual Method	0	0
Impaired Financing Receivable, Unpaid Principal Balance	0	1
Consumer Other Financing Receivable [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	1	0
Impaired Financing Receivable, Recorded Investment	0	0
Impaired Financing Receivable, Related Allowance	0	0
Impaired Financing Receivable, Interest Income, Accrual Method	0	0
Impaired Financing Receivable, Unpaid Principal Balance	0	0
Construction And Land Development [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	0	1
Impaired Financing Receivable, Recorded Investment	0	0
Impaired Financing Receivable, Related Allowance	0	0
Impaired Financing Receivable, Interest Income, Accrual Method	0	0
Impaired Financing Receivable, Unpaid Principal Balance	0	1
Consumer Loan [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	74	65
Impaired Financing Receivable, Recorded Investment	57	72
Impaired Financing Receivable, Related Allowance	2	2
Impaired Financing Receivable, Interest Income, Accrual Method	2	0
Impaired Financing Receivable, Unpaid Principal Balance	66	85
Impaired Financing Receivable Recorded Investment With an Allowance [Member] [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	103	95
Impaired Financing Receivable Recorded Investment With an Allowance [Member] [Member] | Owner Occupied [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	24
Impaired Financing Receivable Recorded Investment With an Allowance [Member] [Member] | Municipal [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	0
Impaired Financing Receivable Recorded Investment With an Allowance [Member] [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	80	65
Impaired Financing Receivable Recorded Investment With an Allowance [Member] [Member] | Term [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	2
Impaired Financing Receivable Recorded Investment With an Allowance [Member] [Member] | Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	2	3
Impaired Financing Receivable Recorded Investment With an Allowance [Member] [Member] | Home Equity Line of Credit [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	3
Impaired Financing Receivable Recorded Investment With an Allowance [Member] [Member] | One Through Four Family Residential [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	18
Impaired Financing Receivable Recorded Investment With an Allowance [Member] [Member] | Construction And Other Consumer Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	0
Impaired Financing Receivable Recorded Investment With an Allowance [Member] [Member] | Consumer Other Financing Receivable [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	0
Impaired Financing Receivable Recorded Investment With an Allowance [Member] [Member] | Construction And Land Development [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	0
Impaired Financing Receivable Recorded Investment With an Allowance [Member] [Member] | Consumer Loan [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	21	27
Impaired Financing Receivable Recorded Investment With No Allowance [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	126	166
Impaired Financing Receivable Recorded Investment With No Allowance [Member] | Commercial And Industrial [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	48	52
Impaired Financing Receivable Recorded Investment With No Allowance [Member] | Owner Occupied [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	27	31
Impaired Financing Receivable Recorded Investment With No Allowance [Member] | Municipal [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	0	1
Impaired Financing Receivable Recorded Investment With No Allowance [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	75	84
Impaired Financing Receivable Recorded Investment With No Allowance [Member] | Term [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	15	37
Impaired Financing Receivable Recorded Investment With No Allowance [Member] | Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	15	37
Impaired Financing Receivable Recorded Investment With No Allowance [Member] | Home Equity Line of Credit [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	10	12
Impaired Financing Receivable Recorded Investment With No Allowance [Member] | One Through Four Family Residential [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	26	32
Impaired Financing Receivable Recorded Investment With No Allowance [Member] | Construction And Other Consumer Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	0	1
Impaired Financing Receivable Recorded Investment With No Allowance [Member] | Consumer Other Financing Receivable [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	0	0
Impaired Financing Receivable Recorded Investment With No Allowance [Member] | Construction And Land Development [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	0	0
Impaired Financing Receivable Recorded Investment With No Allowance [Member] | Consumer Loan [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	36	45
Impaired Financing Receivable Related Allowance [Member] | Commercial And Industrial [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	$ 56	36
Impaired Financing Receivable Related Allowance [Member] | Owner Occupied [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment		29
Impaired Financing Receivable Related Allowance [Member] | Municipal [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment		0
Impaired Financing Receivable Related Allowance [Member] | Term [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment		3
Impaired Financing Receivable Related Allowance [Member] | Home Equity Line of Credit [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment		2
Impaired Financing Receivable Related Allowance [Member] | One Through Four Family Residential [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment		25
Impaired Financing Receivable Related Allowance [Member] | Construction And Other Consumer Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment		0
Impaired Financing Receivable Related Allowance [Member] | Consumer Other Financing Receivable [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment		0
Impaired Financing Receivable Related Allowance [Member] | Construction And Land Development [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment		$ 0