Asset Quality (Details 7) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Credit Risk Profile Based on Payment Activity
Credit risk profile based on payment	$ 49,575	$ 50,107
Consumer Loans [Member]
Credit Risk Profile Based on Payment Activity
Credit risk profile based on payment	14,793	15,587
Consumer Other - Key Community Bank [Member]
Credit Risk Profile Based on Payment Activity
Credit risk profile based on payment	1,192	1,167
Consumer Marine [Member]
Credit Risk Profile Based on Payment Activity
Credit risk profile based on payment	1,766	2,234
Consumer Others [Member]
Credit Risk Profile Based on Payment Activity
Credit risk profile based on payment	125	162
Performing [Member] | Consumer Other - Key Community Bank [Member]
Credit Risk Profile Based on Payment Activity
Credit risk profile based on payment	1,191	1,163
Performing [Member] | Consumer Marine [Member]
Credit Risk Profile Based on Payment Activity
Credit risk profile based on payment	1,735	2,192
Performing [Member] | Consumer Others [Member]
Credit Risk Profile Based on Payment Activity
Credit risk profile based on payment	124	160
Nonperforming [Member] | Consumer Other - Key Community Bank [Member]
Credit Risk Profile Based on Payment Activity
Credit risk profile based on payment	1	4
Nonperforming [Member] | Consumer Marine [Member]
Credit Risk Profile Based on Payment Activity
Credit risk profile based on payment	31	42
Nonperforming [Member] | Consumer Others [Member]
Credit Risk Profile Based on Payment Activity
Credit risk profile based on payment	1	2
Credit Risk Profile [Member] | Consumer Loans [Member]
Credit Risk Profile Based on Payment Activity
Credit risk profile based on payment	3,083	3,563
Credit Risk Profile [Member] | Performing [Member] | Consumer Loans [Member]
Credit Risk Profile Based on Payment Activity
Credit risk profile based on payment	3,050	3,515
Credit Risk Profile [Member] | Nonperforming [Member] | Consumer Loans [Member]
Credit Risk Profile Based on Payment Activity
Credit risk profile based on payment	$ 33	$ 48