The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

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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
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Average Recorded Investment	$ 250	$ 379
Impaired Financing Receivable, Interest Income, Accrual Method	1	8
Allowance for loan losses: Individually evaluated for impairment	(9)		$ (9)
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	488		486
Financing Receivable, Individually Evaluated for Impairment	268		291
Financing Receivable, Collectively Evaluated for Impairment	47,338		46,423
Loans and Leases Receivable, Gross	47,606		46,714
Loans and Leases Receivable, Allowance	497	473	495	$ 518
Owner Occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Average Recorded Investment	60	91
Impaired Financing Receivable, Interest Income, Accrual Method	0	8
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses: Individually evaluated for impairment	(6)		(6)
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	322		325
Financing Receivable, Individually Evaluated for Impairment			164
Financing Receivable, Collectively Evaluated for Impairment			23,998
Loans and Leases Receivable, Gross	24,598		24,162
Loans and Leases Receivable, Allowance	328	329	331	371
Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Average Recorded Investment	0	5
Impaired Financing Receivable, Interest Income, Accrual Method	0	0
Allowance for loan losses: Individually evaluated for impairment	(1)
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	112
Loans and Leases Receivable, Allowance	113	104	110	103
Consumer Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Average Recorded Investment	0	0
Impaired Financing Receivable, Interest Income, Accrual Method	0	0
Allowance for loan losses: Individually evaluated for impairment	(2)		(2)
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	54		52
Financing Receivable, Individually Evaluated for Impairment			72
Financing Receivable, Collectively Evaluated for Impairment			11,355
Loans and Leases Receivable, Gross	11,478		11,427
Loans and Leases Receivable, Allowance	56	40	54	$ 44
Commercial Loan [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Average Recorded Investment	144	240
Impaired Financing Receivable, Interest Income, Accrual Method	1	8
Term [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Average Recorded Investment	35	57
Impaired Financing Receivable, Interest Income, Accrual Method	0	0
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Average Recorded Investment	35	62
Impaired Financing Receivable, Interest Income, Accrual Method	0	0
Allowance for loan losses: Individually evaluated for impairment			(1)
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment			109
Financing Receivable, Individually Evaluated for Impairment			55
Financing Receivable, Collectively Evaluated for Impairment			11,070
Loans and Leases Receivable, Gross	11,530		11,125
Loans and Leases Receivable, Allowance	113		$ 110
Home Equity Line of Credit [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Average Recorded Investment	14	20
Impaired Financing Receivable, Interest Income, Accrual Method	0	0
One Through Four Family Residential [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Average Recorded Investment	55	55
Impaired Financing Receivable, Interest Income, Accrual Method	0	0
Construction And Other Consumer Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Average Recorded Investment	2	2
Impaired Financing Receivable, Interest Income, Accrual Method	0	0
Consumer Loan [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Average Recorded Investment	71	77
Impaired Financing Receivable, Interest Income, Accrual Method	0	0
Municipal [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Average Recorded Investment	1	1
Impaired Financing Receivable, Interest Income, Accrual Method	0	$ 0
Outstanding Loan Balances [Member] \| Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Individually Evaluated for Impairment	148
Financing Receivable, Collectively Evaluated for Impairment	24,450
Outstanding Loan Balances [Member] \| Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Individually Evaluated for Impairment	50
Financing Receivable, Collectively Evaluated for Impairment	11,480
Outstanding Loan Balances [Member] \| Consumer Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Individually Evaluated for Impairment	70
Financing Receivable, Collectively Evaluated for Impairment	$ 11,408