Loans And Allowance For Credit Losses (Summary Of Information On Impaired Loans) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	$ 285		$ 285		$ 310
Impaired Financing Receivable, Recorded Investment	240		240		261
Impaired Financing Receivable, Related Allowance	13		13		8
Average recorded investment	266	$ 299	242	$ 273
Interest income recognized	0	0	2	9
Commercial And Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	132		132		112
Impaired Financing Receivable, Recorded Investment	104		104
Impaired Financing Receivable, Related Allowance	9		9		4
Owner Occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	44		44		67
Impaired Financing Receivable, Recorded Investment	41		41		60
Impaired Financing Receivable, Related Allowance	1		1		2
Average recorded investment	58	51	56	46
Interest income recognized	0	0	0	8
Municipal [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	0		0		1
Impaired Financing Receivable, Recorded Investment	0		0		1
Impaired Financing Receivable, Related Allowance	0		0		0
Average recorded investment	0	1	0	1
Interest income recognized	0	0	0	0
Commercial Loan [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	176		176		180
Impaired Financing Receivable, Recorded Investment	145		145		149
Impaired Financing Receivable, Related Allowance	10		10		6
Average recorded investment	170	176	146	155
Interest income recognized	0	0	2	8
Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Recorded Investment					0
Average recorded investment	0	1	0	1
Interest income recognized	0	0	0	0
Term [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	35		35		44
Impaired Financing Receivable, Recorded Investment	31		31		40
Impaired Financing Receivable, Related Allowance	0		0		0
Average recorded investment	27	49	29	50
Interest income recognized	0	0	0	1
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	35		35		45
Impaired Financing Receivable, Recorded Investment	31		31		40
Impaired Financing Receivable, Related Allowance	0		0		0
Average recorded investment	27	50	29	51
Interest income recognized	0	0	0	1
Home Equity Line of Credit [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	15		15		15
Impaired Financing Receivable, Recorded Investment	14		14		14
Impaired Financing Receivable, Related Allowance	1		1		0
Average recorded investment	14	14	13	13
Interest income recognized	0	0	0	0
One Through Four Family Residential [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	58		58		69
Impaired Financing Receivable, Recorded Investment	50		50		57
Impaired Financing Receivable, Related Allowance	2		2		2
Average recorded investment	53	58	52	53
Interest income recognized	0	0	0	0
Construction And Other Consumer Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	1		1		1
Impaired Financing Receivable, Recorded Investment	0		0		1
Impaired Financing Receivable, Related Allowance	0		0		0
Average recorded investment	2	1	2	1
Interest income recognized	0	0	0
Consumer Loan [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	74		74		85
Impaired Financing Receivable, Recorded Investment	64		64		72
Impaired Financing Receivable, Related Allowance	3		3		2
Average recorded investment	69	73	67	67
Interest income recognized	0	0	0	0
Impaired Financing Receivable Related Allowance [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Recorded Investment	115		115		95
Impaired Financing Receivable Related Allowance [Member] | Commercial And Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Recorded Investment	68		68		36
Impaired Financing Receivable Related Allowance [Member] | Owner Occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Recorded Investment					29
Impaired Financing Receivable Related Allowance [Member] | Municipal [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Recorded Investment					0
Impaired Financing Receivable Related Allowance [Member] | Commercial Loan [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Recorded Investment	84		84		65
Impaired Financing Receivable Related Allowance [Member] | Term [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Recorded Investment					3
Impaired Financing Receivable Related Allowance [Member] | Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Recorded Investment	5		5		3
Impaired Financing Receivable Related Allowance [Member] | Home Equity Line of Credit [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Recorded Investment					2
Impaired Financing Receivable Related Allowance [Member] | One Through Four Family Residential [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Recorded Investment					25
Impaired Financing Receivable Related Allowance [Member] | Construction And Other Consumer Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Recorded Investment					0
Impaired Financing Receivable Related Allowance [Member] | Consumer Loan [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Recorded Investment	26		26		27
Impaired Financing Receivable Recorded Investment With No Allowance [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Recorded Investment	125		125		166
Impaired Financing Receivable Recorded Investment With No Allowance [Member] | Commercial And Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Recorded Investment	36		36		52
Impaired Financing Receivable Recorded Investment With No Allowance [Member] | Owner Occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Recorded Investment	25		25		31
Impaired Financing Receivable Recorded Investment With No Allowance [Member] | Municipal [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Recorded Investment	0		0		1
Impaired Financing Receivable Recorded Investment With No Allowance [Member] | Commercial Loan [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Recorded Investment	61		61		84
Impaired Financing Receivable Recorded Investment With No Allowance [Member] | Term [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Recorded Investment	26		26		37
Impaired Financing Receivable Recorded Investment With No Allowance [Member] | Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Recorded Investment	26		26		37
Impaired Financing Receivable Recorded Investment With No Allowance [Member] | Home Equity Line of Credit [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Recorded Investment	11		11		12
Impaired Financing Receivable Recorded Investment With No Allowance [Member] | One Through Four Family Residential [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Recorded Investment	27		27		32
Impaired Financing Receivable Recorded Investment With No Allowance [Member] | Construction And Other Consumer Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Recorded Investment	0		0		1
Impaired Financing Receivable Recorded Investment With No Allowance [Member] | Consumer Loan [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Recorded Investment	38		38		45
Commercial and Industrial Sector [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Recorded Investment					$ 88
Average recorded investment	112		90
Interest income recognized	$ 0		$ 2
Commercial and Industrial Sector [Member] | Commercial And Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Average recorded investment		124		108
Interest income recognized		$ 0		$ 0