Loans And Allowance For Credit Losses (Summary Of Information On Impaired Loans) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Impaired [Line Items]
Current Fiscal Year End Date	--12-31
Impaired Financing Receivable, Average Recorded Investment	$ 520	$ 603
Impaired Financing Receivable, Recorded Investment	461	660
Impaired Financing Receivable, Related Allowance	30	63
Impaired Financing Receivable, Interest Income, Accrual Method	27	32
Impaired Financing Receivable, Unpaid Principal Balance	573	788
Commercial And Industrial [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	289	333
Impaired Financing Receivable, Recorded Investment	222	393
Impaired Financing Receivable, Related Allowance	24	52
Impaired Financing Receivable, Interest Income, Accrual Method	6	5
Impaired Financing Receivable, Unpaid Principal Balance	293	470
Owner Occupied [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	97	99
Impaired Financing Receivable, Recorded Investment	102	101
Impaired Financing Receivable, Related Allowance	2	3
Impaired Financing Receivable, Interest Income, Accrual Method	6	9
Impaired Financing Receivable, Unpaid Principal Balance	120	115
Municipal [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	1	1
Impaired Financing Receivable, Recorded Investment	1	1
Impaired Financing Receivable, Related Allowance	0	0
Impaired Financing Receivable, Interest Income, Accrual Method	0	0
Impaired Financing Receivable, Unpaid Principal Balance	1	1
Commercial Portfolio Segment [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	387	433
Impaired Financing Receivable, Recorded Investment	325	495
Impaired Financing Receivable, Related Allowance	26	55
Impaired Financing Receivable, Interest Income, Accrual Method	12	14
Impaired Financing Receivable, Unpaid Principal Balance	414	586
Term [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	49	76
Impaired Financing Receivable, Recorded Investment	48	70
Impaired Financing Receivable, Related Allowance	0	2
Impaired Financing Receivable, Interest Income, Accrual Method	12	13
Impaired Financing Receivable, Unpaid Principal Balance	56	92
Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	57	87
Impaired Financing Receivable, Recorded Investment	54	83
Impaired Financing Receivable, Related Allowance	0	2
Impaired Financing Receivable, Interest Income, Accrual Method	12	15
Impaired Financing Receivable, Unpaid Principal Balance	64	114
Home Equity Line of Credit [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	21	22
Impaired Financing Receivable, Recorded Investment	22	23
Impaired Financing Receivable, Related Allowance	0	0
Impaired Financing Receivable, Interest Income, Accrual Method	1	1
Impaired Financing Receivable, Unpaid Principal Balance	25	24
One Through Four Family Residential [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	52	57
Impaired Financing Receivable, Recorded Investment	57	55
Impaired Financing Receivable, Related Allowance	4	6
Impaired Financing Receivable, Interest Income, Accrual Method	1	2
Impaired Financing Receivable, Unpaid Principal Balance	67	59
Construction And Other Consumer Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	2	2
Impaired Financing Receivable, Recorded Investment	2	3
Impaired Financing Receivable, Related Allowance	0	0
Impaired Financing Receivable, Interest Income, Accrual Method	0	0
Impaired Financing Receivable, Unpaid Principal Balance	2	3
Consumer Other Financing Receivable [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	1	2
Impaired Financing Receivable, Recorded Investment	1	1
Impaired Financing Receivable, Related Allowance	0	0
Impaired Financing Receivable, Interest Income, Accrual Method	1	0
Impaired Financing Receivable, Unpaid Principal Balance	1	2
Commercial Real Estate Construction [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	8	11
Impaired Financing Receivable, Recorded Investment	6	13
Impaired Financing Receivable, Related Allowance	0	0
Impaired Financing Receivable, Interest Income, Accrual Method	0	2
Impaired Financing Receivable, Unpaid Principal Balance	8	22
Consumer Loan [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	76	83
Impaired Financing Receivable, Recorded Investment	82	82
Impaired Financing Receivable, Related Allowance	4	6
Impaired Financing Receivable, Interest Income, Accrual Method	3	3
Impaired Financing Receivable, Unpaid Principal Balance	95	88
Impaired Financing Receivable Recorded Investment With an Allowance [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	218	401
Impaired Financing Receivable Recorded Investment With an Allowance [Member] | Owner Occupied [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	23
Impaired Financing Receivable Recorded Investment With an Allowance [Member] | Municipal [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	0
Impaired Financing Receivable Recorded Investment With an Allowance [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	165	341
Impaired Financing Receivable Recorded Investment With an Allowance [Member] | Term [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	12
Impaired Financing Receivable Recorded Investment With an Allowance [Member] | Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	14	23
Impaired Financing Receivable Recorded Investment With an Allowance [Member] | Home Equity Line of Credit [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	9
Impaired Financing Receivable Recorded Investment With an Allowance [Member] | One Through Four Family Residential [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	29
Impaired Financing Receivable Recorded Investment With an Allowance [Member] | Construction And Other Consumer Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	1
Impaired Financing Receivable Recorded Investment With an Allowance [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] | Commercial Real Estate Construction [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	2
Impaired Financing Receivable Recorded Investment With an Allowance [Member] | Consumer Loan [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	39	37
Impaired Financing Receivable Recorded Investment With No Allowance [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	243	259
Impaired Financing Receivable Recorded Investment With No Allowance [Member] | Commercial And Industrial [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	80	82
Impaired Financing Receivable Recorded Investment With No Allowance [Member] | Owner Occupied [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	79	71
Impaired Financing Receivable Recorded Investment With No Allowance [Member] | Municipal [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	1	1
Impaired Financing Receivable Recorded Investment With No Allowance [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	160	154
Impaired Financing Receivable Recorded Investment With No Allowance [Member] | Term [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	36	53
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	40	60
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	13	16
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	28	27
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	1	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	1	1
Impaired Financing Receivable Recorded Investment With No Allowance [Member] | Commercial Real Estate Construction [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	4	7
Impaired Financing Receivable Recorded Investment With No Allowance [Member] | Consumer Loan [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	43	45
Impaired Financing Receivable Related Allowance [Member] | Commercial And Industrial [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment	$ 142	311
Impaired Financing Receivable Related Allowance [Member] | Owner Occupied [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment		30
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		17
Impaired Financing Receivable Related Allowance [Member] | Home Equity Line of Credit [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment		7
Impaired Financing Receivable Related Allowance [Member] | One Through Four Family Residential [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment		28
Impaired Financing Receivable Related Allowance [Member] | Construction And Other Consumer Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment		2
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] | Commercial Real Estate Construction [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment		$ 6