Asset Quality (Details 7) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Jun. 30, 2011
Credit Risk Profile Based on Payment Activity
Credit risk profile based on payment	$ 49,605	$ 47,840
Consumer Loans [Member]
Credit Risk Profile Based on Payment Activity
Credit risk profile based on payment	15,002	15,152
Consumer other - Key Community Bank [Member]
Credit Risk Profile Based on Payment Activity
Credit risk profile based on payment	1,263	1,157
Consumer Marine [Member]
Credit Risk Profile Based on Payment Activity
Credit risk profile based on payment	1,542	1,989
Consumer Others [Member]
Credit Risk Profile Based on Payment Activity
Credit risk profile based on payment	101	142
Performing [Member] | Consumer other - Key Community Bank [Member]
Credit Risk Profile Based on Payment Activity
Credit risk profile based on payment	1,261	1,154
Performing [Member] | Consumer Marine [Member]
Credit Risk Profile Based on Payment Activity
Credit risk profile based on payment	1,523	1,957
Performing [Member] | Consumer Others [Member]
Credit Risk Profile Based on Payment Activity
Credit risk profile based on payment	100	141
Nonperforming [Member] | Consumer other - Key Community Bank [Member]
Credit Risk Profile Based on Payment Activity
Credit risk profile based on payment	2	3
Nonperforming [Member] | Consumer Marine [Member]
Credit Risk Profile Based on Payment Activity
Credit risk profile based on payment	19	32
Nonperforming [Member] | Consumer Others [Member]
Credit Risk Profile Based on Payment Activity
Credit risk profile based on payment	1	1
Credit Risk Profile [Member] | Consumer Loans [Member]
Credit Risk Profile Based on Payment Activity
Credit risk profile based on payment	2,906	3,288
Credit Risk Profile [Member] | Performing [Member] | Consumer Loans [Member]
Credit Risk Profile Based on Payment Activity
Credit risk profile based on payment	2,884	3,252
Credit Risk Profile [Member] | Nonperforming [Member] | Consumer Loans [Member]
Credit Risk Profile Based on Payment Activity
Credit risk profile based on payment	$ 22	$ 36