Asset Quality (Details 1) (USD $) In Millions, unless otherwise specified	6 Months Ended		12 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Financing Receivable, Impaired [Line Items]
With no related allowance recorded, Recorded Investment	$ 223	$ 322	$ 218
With no related allowance recorded, Unpaid Principal Balance	546	650	548
With no related allowance recorded, Average Recorded Investment	231	356	304
With related allowance recorded, Recorded Investment	188	166	170
With related allowance recorded, Unpaid Principal Balance	241	318	203
With related allowance recorded, Specific Allowance	48	46	51
With related allowance recorded, Average Recorded Investment	156	199	201
Recorded Investment	411	488	388
Unpaid Principal Balance	787	968	751
Average Recorded Investment	387	555	505
Commercial, financial and agricultural [Member]
Financing Receivable, Impaired [Line Items]
With no related allowance recorded, Recorded Investment	59	116	88
With no related allowance recorded, Unpaid Principal Balance	142	217	195
With no related allowance recorded, Average Recorded Investment	68	89	75
With related allowance recorded, Recorded Investment	43	43	62
With related allowance recorded, Unpaid Principal Balance	53	71	70
With related allowance recorded, Specific Allowance	12	14	26
With related allowance recorded, Average Recorded Investment	46	66	75
Commercial real estate: Commercial Mortgage [Member]
Financing Receivable, Impaired [Line Items]
With no related allowance recorded, Recorded Investment	112	123	100
With no related allowance recorded, Unpaid Principal Balance	199	207	240
With no related allowance recorded, Average Recorded Investment	113	143	131
With related allowance recorded, Recorded Investment	56	89	96
With related allowance recorded, Unpaid Principal Balance	98	174	115
With related allowance recorded, Specific Allowance	15	21	21
With related allowance recorded, Average Recorded Investment	63	88	91
Commercial real estate: Construction [Member]
Financing Receivable, Impaired [Line Items]
With no related allowance recorded, Recorded Investment	51	83	30
With no related allowance recorded, Unpaid Principal Balance	204	226	113
With no related allowance recorded, Average Recorded Investment	49	124	98
With related allowance recorded, Recorded Investment	4	34	12
With related allowance recorded, Unpaid Principal Balance	4	73	18
With related allowance recorded, Specific Allowance	3	11	4
With related allowance recorded, Average Recorded Investment	4	39	29
Commercial Real Estate Loans [Member]
Financing Receivable, Impaired [Line Items]
With no related allowance recorded, Recorded Investment	163	206	130
With no related allowance recorded, Unpaid Principal Balance	403	433	353
With no related allowance recorded, Average Recorded Investment	162	267	229
With related allowance recorded, Recorded Investment	60	123	108
With related allowance recorded, Unpaid Principal Balance	102	247	133
With related allowance recorded, Specific Allowance	18	32	25
With related allowance recorded, Average Recorded Investment	67	127	120
Commercial Lease Financing [Member]
Financing Receivable, Impaired [Line Items]
With related allowance recorded, Recorded Investment		0
With related allowance recorded, Unpaid Principal Balance		0
With related allowance recorded, Specific Allowance		0
With related allowance recorded, Average Recorded Investment		6
Commercial Loans [Member]
Financing Receivable, Impaired [Line Items]
With no related allowance recorded, Recorded Investment	222
With no related allowance recorded, Unpaid Principal Balance	545
With no related allowance recorded, Average Recorded Investment	230
With related allowance recorded, Recorded Investment	103
With related allowance recorded, Unpaid Principal Balance	155
With related allowance recorded, Specific Allowance	30
With related allowance recorded, Average Recorded Investment	113
Real estate - residential mortgage [Member]
Financing Receivable, Impaired [Line Items]
With no related allowance recorded, Recorded Investment	1
With no related allowance recorded, Unpaid Principal Balance	1
With no related allowance recorded, Average Recorded Investment	1
With related allowance recorded, Recorded Investment	16
With related allowance recorded, Unpaid Principal Balance	17
With related allowance recorded, Specific Allowance	2
With related allowance recorded, Average Recorded Investment	8
Home Equity Key Community Bank [Member]
Financing Receivable, Impaired [Line Items]
With related allowance recorded, Recorded Investment	11
With related allowance recorded, Unpaid Principal Balance	11
With related allowance recorded, Specific Allowance	3
With related allowance recorded, Average Recorded Investment	6
Home Equity Other [Member]
Financing Receivable, Impaired [Line Items]
With related allowance recorded, Recorded Investment	6
With related allowance recorded, Unpaid Principal Balance	6
With related allowance recorded, Specific Allowance	1
With related allowance recorded, Average Recorded Investment	3
Home Equity Loans [Member]
Financing Receivable, Impaired [Line Items]
With related allowance recorded, Recorded Investment	17
With related allowance recorded, Unpaid Principal Balance	17
With related allowance recorded, Specific Allowance	4
With related allowance recorded, Average Recorded Investment	9
Consumer other - Key Community Bank [Member]
Financing Receivable, Impaired [Line Items]
With related allowance recorded, Recorded Investment	2
With related allowance recorded, Unpaid Principal Balance	2
With related allowance recorded, Specific Allowance	1
With related allowance recorded, Average Recorded Investment	1
Consumer Marine [Member]
Financing Receivable, Impaired [Line Items]
With related allowance recorded, Recorded Investment	50
With related allowance recorded, Unpaid Principal Balance	50
With related allowance recorded, Specific Allowance	11
With related allowance recorded, Average Recorded Investment	25
Other Consumer [Member]
Financing Receivable, Impaired [Line Items]
With related allowance recorded, Recorded Investment
With related allowance recorded, Unpaid Principal Balance
With related allowance recorded, Specific Allowance
With related allowance recorded, Average Recorded Investment
Consumer Other [Member]
Financing Receivable, Impaired [Line Items]
With related allowance recorded, Recorded Investment	50
With related allowance recorded, Unpaid Principal Balance	50
With related allowance recorded, Specific Allowance	11
With related allowance recorded, Average Recorded Investment	25
Consumer Loans [Member]
Financing Receivable, Impaired [Line Items]
With no related allowance recorded, Recorded Investment	(1)
With no related allowance recorded, Unpaid Principal Balance	(1)
With no related allowance recorded, Average Recorded Investment	(1)
With related allowance recorded, Recorded Investment	85
With related allowance recorded, Unpaid Principal Balance	86
With related allowance recorded, Specific Allowance	18
With related allowance recorded, Average Recorded Investment	$ 43