Loans And Allowance For Credit Losses (Summary Of ALLL And Outstanding Loan Balances According To The Company's Impairment Method) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2015
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Average Recorded Investment	$ 660	$ 743	$ 611	$ 630
Impaired Financing Receivable, Interest Income, Accrual Method	13	9	18	18
Allowance for loan losses: Individually evaluated for impairment	(46)		(46)			$ (65)
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	498		498			502
Outstanding loan balances: Individually evaluated for impairment	563		563			619
Outstanding loan balances: Collectively evaluated for impairment	43,077		43,077			41,953
Certain Loans and Debt Securities Acquired in Transfer, with Related Allowance for Credit Losses Due to Subsequent Impairment	43		43			77
Loans and Leases Receivable, Gross	43,683		43,683			42,649
Financing Receivable Allowance For Credit Losses and Receivables Acquired With Deteriorated Credit Quality	0		0			0
Loans and Leases Receivable, Allowance	544	608	544	608	$ 544	567	$ 612	$ 606
Owner Occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Average Recorded Investment	109	111	102	113
Impaired Financing Receivable, Interest Income, Accrual Method	1	3	4	6
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Individually evaluated for impairment	(40)		(40)			(56)
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	353		353			364
Outstanding loan balances: Individually evaluated for impairment	411		411			466
Outstanding loan balances: Collectively evaluated for impairment	21,765		21,765			21,111
Certain Loans and Debt Securities Acquired in Transfer, with Related Allowance for Credit Losses Due to Subsequent Impairment	27		27			38
Loans and Leases Receivable, Gross	22,203		22,203			21,615
Financing Receivable Allowance For Credit Losses and Receivables Acquired With Deteriorated Credit Quality	0		0			0
Loans and Leases Receivable, Allowance	393	456	393	456	397	420	464	454
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Average Recorded Investment	11	12	11	12
Impaired Financing Receivable, Interest Income, Accrual Method	0	1	0	1
Loans and Leases Receivable, Allowance	116	122	116	122	114	116	118	114
Consumer Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Average Recorded Investment	1	2	1	2
Impaired Financing Receivable, Interest Income, Accrual Method	0	0	0	0
Allowance for loan losses: Individually evaluated for impairment	(5)		(5)			(6)
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	30		30			25
Outstanding loan balances: Individually evaluated for impairment	77		77			75
Outstanding loan balances: Collectively evaluated for impairment	10,199		10,199			9,611
Certain Loans and Debt Securities Acquired in Transfer, with Related Allowance for Credit Losses Due to Subsequent Impairment	6		6			7
Loans and Leases Receivable, Gross	10,282		10,282			9,693
Financing Receivable Allowance For Credit Losses and Receivables Acquired With Deteriorated Credit Quality	0		0			0
Loans and Leases Receivable, Allowance	35	30	35	30	$ 33	31	$ 30	$ 38
Commercial Loan [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Average Recorded Investment	508	542	459	431
Impaired Financing Receivable, Interest Income, Accrual Method	5	4	8	8
Term [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Average Recorded Investment	59	98	60	97
Impaired Financing Receivable, Interest Income, Accrual Method	7	3	9	7
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Average Recorded Investment	70	110	71	109
Impaired Financing Receivable, Interest Income, Accrual Method	7	4	9	8
Allowance for loan losses: Individually evaluated for impairment	(1)		(1)			(3)
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	115		115			113
Outstanding loan balances: Individually evaluated for impairment	75		75			78
Outstanding loan balances: Collectively evaluated for impairment	11,113		11,113			11,231
Certain Loans and Debt Securities Acquired in Transfer, with Related Allowance for Credit Losses Due to Subsequent Impairment	10		10			32
Loans and Leases Receivable, Gross	11,198		11,198			11,341
Financing Receivable Allowance For Credit Losses and Receivables Acquired With Deteriorated Credit Quality	0		0			0
Loans and Leases Receivable, Allowance	116		116			$ 116
Home Equity Line of Credit [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Average Recorded Investment	21	25	21	24
Impaired Financing Receivable, Interest Income, Accrual Method	0	0	0	1
One Through Four Family Residential [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Average Recorded Investment	58	61	56	61
Impaired Financing Receivable, Interest Income, Accrual Method	1	1	1	1
Construction And Other Consumer Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Average Recorded Investment	2	3	3	3
Impaired Financing Receivable, Interest Income, Accrual Method	0	0	0	0
Consumer Loan [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Average Recorded Investment	82	91	81	90
Impaired Financing Receivable, Interest Income, Accrual Method	1	1	1	2
Municipal [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Average Recorded Investment	1	1	1	1
Impaired Financing Receivable, Interest Income, Accrual Method	$ 0	$ 0	$ 0	$ 0