Asset Quality (Details 10) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Jun. 30, 2011
Financing Receivable, Allowance for Credit Loss, Additional Information
Individually Evaluated for Impairment Allowance	$ 48	$ 46
Collectively Evaluated for Impairment Allowance	840	1,184
Loans Outstanding	49,605	47,840
Individually Evaluated for Impairment corresponding allowance	411	488
Collectively Evaluated for Impairment, Outstanding	49,194	47,352
Collectively Evaluated for Impairment Allowance, Discontinued Operations	79	109
Loans Outstanding, Discontinued Operations	5,483	6,261
Collectively Evaluated for Impairment Outstanding, Discontinued Operations	5,483	6,261
Individually Evaluated for Impairment Allowance, Total ALLL - Including Discontinued Operations	48	46
Collectively Evaluated for Impairment Allowance, Total ALLL - Including Discontinued Operations	919	1,293
Loans Outstanding Total ALLL - Including Discontinued Operations	55,088	54,101
Individually Evaluated for Impairment Outstanding Total ALLL - Including Discontinued Operations	411	488
Collectively Evaluated for Impairment Outstanding Total ALLL - Including Discontinued Operations	54,677	53,613
Commercial, financial and agricultural [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information
Individually Evaluated for Impairment Allowance	12	14
Collectively Evaluated for Impairment Allowance	292	381
Loans Outstanding	20,386	16,883
Individually Evaluated for Impairment corresponding allowance	102	159
Collectively Evaluated for Impairment, Outstanding	20,284	16,724
Commercial real estate: Commercial Mortgage [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information
Individually Evaluated for Impairment Allowance	15	21
Collectively Evaluated for Impairment Allowance	235	322
Loans Outstanding	7,409	8,069
Individually Evaluated for Impairment corresponding allowance	168	213
Collectively Evaluated for Impairment, Outstanding	7,241	7,856
Commercial real estate: Construction [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information
Individually Evaluated for Impairment Allowance	3	11
Collectively Evaluated for Impairment Allowance	52	95
Loans Outstanding	1,172	1,631
Individually Evaluated for Impairment corresponding allowance	55	116
Collectively Evaluated for Impairment, Outstanding	1,117	1,515
Commercial Real Estate Loans [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information
Individually Evaluated for Impairment Allowance	18	32
Collectively Evaluated for Impairment Allowance	287	417
Loans Outstanding	8,581	9,700
Individually Evaluated for Impairment corresponding allowance	223	329
Collectively Evaluated for Impairment, Outstanding	8,358	9,371
Commercial Lease Financing [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information
Collectively Evaluated for Impairment Allowance	68	107
Loans Outstanding	5,636	6,105
Collectively Evaluated for Impairment, Outstanding	5,636	6,105
Commercial [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information
Individually Evaluated for Impairment Allowance	30	46
Collectively Evaluated for Impairment Allowance	647	905
Loans Outstanding	34,603	32,688
Individually Evaluated for Impairment corresponding allowance	325	488
Collectively Evaluated for Impairment, Outstanding	34,278	32,200
Real estate - residential mortgage [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information
Individually Evaluated for Impairment Allowance	2
Collectively Evaluated for Impairment Allowance	24	41
Loans Outstanding	2,016	1,838
Individually Evaluated for Impairment corresponding allowance	17
Collectively Evaluated for Impairment, Outstanding	1,999	1,838
Home Equity Key Community Bank [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information
Individually Evaluated for Impairment Allowance	3
Collectively Evaluated for Impairment Allowance	77	99
Loans Outstanding	9,601	9,431
Individually Evaluated for Impairment corresponding allowance	11
Collectively Evaluated for Impairment, Outstanding	9,590	9,431
Home Equity Other [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information
Individually Evaluated for Impairment Allowance	1
Collectively Evaluated for Impairment Allowance	23	37
Loans Outstanding	479	595
Individually Evaluated for Impairment corresponding allowance	6
Collectively Evaluated for Impairment, Outstanding	473	595
Home Equity [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information
Individually Evaluated for Impairment Allowance	4
Collectively Evaluated for Impairment Allowance	100	136
Loans Outstanding	10,080	10,026
Individually Evaluated for Impairment corresponding allowance	17
Collectively Evaluated for Impairment, Outstanding	10,063	10,026
Consumer other - Key Community Bank [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information
Individually Evaluated for Impairment Allowance	1
Collectively Evaluated for Impairment Allowance	33	47
Loans Outstanding	1,263	1,157
Individually Evaluated for Impairment corresponding allowance	2
Collectively Evaluated for Impairment, Outstanding	1,261	1,157
Consumer Marine [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information
Individually Evaluated for Impairment Allowance	11
Collectively Evaluated for Impairment Allowance	33	52
Loans Outstanding	1,542	1,989
Individually Evaluated for Impairment corresponding allowance	50
Collectively Evaluated for Impairment, Outstanding	1,492	1,989
Consumer Others [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information
Collectively Evaluated for Impairment Allowance	3	3
Loans Outstanding	101	142
Collectively Evaluated for Impairment, Outstanding	101	142
Consumer Other - Key Corporate Bank [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information
Individually Evaluated for Impairment Allowance	11
Collectively Evaluated for Impairment Allowance	36	55
Loans Outstanding	1,643	2,131
Individually Evaluated for Impairment corresponding allowance	50
Collectively Evaluated for Impairment, Outstanding	1,593	2,131
Consumer Loans [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information
Individually Evaluated for Impairment Allowance	18
Collectively Evaluated for Impairment Allowance	193	279
Loans Outstanding	15,002	15,152
Individually Evaluated for Impairment corresponding allowance	86
Collectively Evaluated for Impairment, Outstanding	$ 14,916	$ 15,152