Loans And Allowance For Credit Losses (Summary Of Information On Impaired Loans) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, Gross, Consumer, Home Equity	$ 2,745		$ 2,745		$ 2,645
Unpaid principal balance	597		597		788
Recorded investment	515		515		660
Impaired Financing Receivable, Related Allowance	32		32		63
Average recorded investment	601	$ 724	559	$ 599
Interest income recognized	5	8	23	26
Owner Occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	117		117		115
Recorded investment	103		103		101
Impaired Financing Receivable, Related Allowance	3		3		3
Average recorded investment	104	100	101	103
Interest income recognized	2	2	5	8
Municipal [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	1		1		1
Recorded investment	1		1		1
Impaired Financing Receivable, Related Allowance	0		0		0
Average recorded investment	1	1	1	1
Interest income recognized	0	0	0	0
Commercial Loan [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	431		431		586
Recorded investment	373		373		495
Impaired Financing Receivable, Related Allowance	28		28		55
Average recorded investment	461	550	413	423
Interest income recognized	3	3	10	12
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	10		10		22
Recorded investment	9		9		13
Impaired Financing Receivable, Related Allowance	0		0		0
Average recorded investment	10	11	11	12
Interest income recognized	0	1	0	2
Term [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	67		67		92
Recorded investment	57		57		70
Impaired Financing Receivable, Related Allowance	0		0		2
Average recorded investment	53	74	58	79
Interest income recognized	1	3	11	9
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	77		77		114
Recorded investment	66		66		83
Impaired Financing Receivable, Related Allowance	0		0		2
Average recorded investment	63	85	69	91
Interest income recognized	1	4	11	11
Home Equity Line of Credit [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	24		24		24
Recorded investment	21		21		23
Impaired Financing Receivable, Related Allowance	0		0		0
Average recorded investment	21	23	21	22
Interest income recognized	0	0	1	1
Consumer Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, Gross, Consumer, Home Equity	2,745		2,745		2,645
Unpaid principal balance	1		1		2
Recorded investment	1		1		1
Impaired Financing Receivable, Related Allowance	0		0		0
Average recorded investment	1	2	1	2
Interest income recognized	0	0	0	0
One Through Four Family Residential [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	61		61		59
Recorded investment	51		51		55
Impaired Financing Receivable, Related Allowance	4		4		6
Average recorded investment	53	61	53	58
Interest income recognized	1	1	1	2
Construction And Other Consumer Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	3		3		3
Recorded investment	3		3		3
Impaired Financing Receivable, Related Allowance	0		0		0
Average recorded investment	2	3	2	3
Interest income recognized	0	0	0	0
Consumer Loan [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	89		89		88
Recorded investment	76		76		82
Impaired Financing Receivable, Related Allowance	4		4		6
Average recorded investment	77	89	77	85
Interest income recognized	1	1	2	3
Impaired Financing Receivable Related Allowance [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded investment	249		249		401
Impaired Financing Receivable Related Allowance [Member] | Owner Occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded investment	39		39		30
Impaired Financing Receivable Related Allowance [Member] | Municipal [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded investment	0		0		0
Impaired Financing Receivable Related Allowance [Member] | Commercial Loan [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded investment	199		199		341
Impaired Financing Receivable Related Allowance [Member] | Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded investment	4		4		6
Impaired Financing Receivable Related Allowance [Member] | Term [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded investment	12		12		17
Impaired Financing Receivable Related Allowance [Member] | Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded investment	16		16		23
Impaired Financing Receivable Related Allowance [Member] | Home Equity Line of Credit [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded investment	8		8		7
Impaired Financing Receivable Related Allowance [Member] | Consumer Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded investment	0		0		0
Impaired Financing Receivable Related Allowance [Member] | One Through Four Family Residential [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded investment	25		25		28
Impaired Financing Receivable Related Allowance [Member] | Construction And Other Consumer Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded investment	1		1		2
Impaired Financing Receivable Related Allowance [Member] | Consumer Loan [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded investment	34		34		37
Impaired Financing Receivable Recorded Investment With No Allowance [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded investment	266		266		259
Impaired Financing Receivable Recorded Investment With No Allowance [Member] | Owner Occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded investment	64		64		71
Impaired Financing Receivable Recorded Investment With No Allowance [Member] | Municipal [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded investment	1		1		1
Impaired Financing Receivable Recorded Investment With No Allowance [Member] | Commercial Loan [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded investment	174		174		154
Impaired Financing Receivable Recorded Investment With No Allowance [Member] | Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded investment	5		5		7
Impaired Financing Receivable Recorded Investment With No Allowance [Member] | Term [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded investment	45		45		53
Impaired Financing Receivable Recorded Investment With No Allowance [Member] | Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded investment	50		50		60
Impaired Financing Receivable Recorded Investment With No Allowance [Member] | Home Equity Line of Credit [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded investment	13		13		16
Impaired Financing Receivable Recorded Investment With No Allowance [Member] | Consumer Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded investment	1		1		1
Impaired Financing Receivable Recorded Investment With No Allowance [Member] | One Through Four Family Residential [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded investment	26		26		27
Impaired Financing Receivable Recorded Investment With No Allowance [Member] | Construction And Other Consumer Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded investment	2		2		1
Impaired Financing Receivable Recorded Investment With No Allowance [Member] | Consumer Loan [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded investment	42		42		45
Commercial and Industrial Sector [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	313		313		470
Recorded investment	269		269		393
Impaired Financing Receivable, Related Allowance	25		25		52
Average recorded investment	356	449	311	319
Interest income recognized	1	$ 1	5	$ 4
Commercial and Industrial Sector [Member] | Impaired Financing Receivable Related Allowance [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded investment	160		160		311
Commercial and Industrial Sector [Member] | Impaired Financing Receivable Recorded Investment With No Allowance [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded investment	$ 109		$ 109		$ 82