Asset Quality (Details 1) (USD $) In Millions	Sep. 30, 2011
Financing Receivable, Impaired [Line Items]
Recorded Investment	$ 1,234
Unpaid Principal Balance	653
Related Allowance	119
Average Recorded Investment	1,287
Commercial Real Estate Loans [Member] | Impaired Financing Receivable With Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	257
Unpaid Principal Balance	172
Related Allowance	61
Average Recorded Investment	294
Commercial Real Estate Loans [Member] | Impaired Financing Receivable With No Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	495
Unpaid Principal Balance	197
Related Allowance	0
Average Recorded Investment	497
Commercial Lease Financing [Member] | Impaired Financing Receivable With Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	34
Unpaid Principal Balance	20
Related Allowance	10
Average Recorded Investment	36
Commercial Lease Financing [Member] | Impaired Financing Receivable With No Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	0
Unpaid Principal Balance	0
Related Allowance	0
Average Recorded Investment	0
Commercial Loans [Member] | Impaired Financing Receivable With Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	435
Unpaid Principal Balance	279
Related Allowance	107
Average Recorded Investment	475
Commercial Loans [Member] | Impaired Financing Receivable With No Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	697
Unpaid Principal Balance	288
Related Allowance	0
Average Recorded Investment	714
Home Equity Loans [Member] | Impaired Financing Receivable With Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	21
Unpaid Principal Balance	21
Related Allowance	7
Average Recorded Investment	22
Home Equity Loans [Member] | Impaired Financing Receivable With No Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	2
Unpaid Principal Balance	0
Related Allowance	0
Average Recorded Investment	2
Commercial, financial and agricultural [Member] | Impaired Financing Receivable With Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	144
Unpaid Principal Balance	87
Related Allowance	36
Average Recorded Investment	145
Commercial, financial and agricultural [Member] | Impaired Financing Receivable With No Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	202
Unpaid Principal Balance	91
Related Allowance	0
Average Recorded Investment	217
Commercial real estate: Commercial Mortgage [Member] | Impaired Financing Receivable With Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	171
Unpaid Principal Balance	134
Related Allowance	42
Average Recorded Investment	193
Commercial real estate: Commercial Mortgage [Member] | Impaired Financing Receivable With No Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	292
Unpaid Principal Balance	140
Related Allowance	0
Average Recorded Investment	267
Commercial real estate: Construction [Member] | Impaired Financing Receivable With Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	86
Unpaid Principal Balance	38
Related Allowance	19
Average Recorded Investment	101
Commercial real estate: Construction [Member] | Impaired Financing Receivable With No Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	203
Unpaid Principal Balance	57
Related Allowance	0
Average Recorded Investment	230
Real estate - residential mortgage [Member] | Impaired Financing Receivable With Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	51
Unpaid Principal Balance	38
Related Allowance	3
Average Recorded Investment	48
Real estate - residential mortgage [Member] | Impaired Financing Receivable With No Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	0
Unpaid Principal Balance	0
Related Allowance	0
Average Recorded Investment	0
Home Equity Key Community Bank [Member] | Impaired Financing Receivable With Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	21
Unpaid Principal Balance	21
Related Allowance	7
Average Recorded Investment	22
Home Equity Key Community Bank [Member] | Impaired Financing Receivable With No Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	2
Unpaid Principal Balance	0
Related Allowance	0
Average Recorded Investment	2
Home Equity Other [Member] | Impaired Financing Receivable With Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	0
Unpaid Principal Balance	0
Related Allowance	0
Average Recorded Investment	0
Home Equity Other [Member] | Impaired Financing Receivable With No Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	0
Unpaid Principal Balance	0
Related Allowance	0
Average Recorded Investment	0
Consumer other - Key Community Bank [Member] | Impaired Financing Receivable With Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	28
Unpaid Principal Balance	27
Related Allowance	2
Average Recorded Investment	26
Consumer other - Key Community Bank [Member] | Impaired Financing Receivable With No Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	0
Unpaid Principal Balance	0
Related Allowance	0
Average Recorded Investment	0
Impaired Financing Receivable With Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	535
Unpaid Principal Balance	365
Related Allowance	119
Average Recorded Investment	571
Impaired Financing Receivable With No Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	699
Unpaid Principal Balance	288
Related Allowance	0
Average Recorded Investment	$ 716