Asset Quality (Details 3) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Concession types for our commercial accruing and nonaccruing TDRs
Interest rate reduction	$ 177	$ 188
Forgiveness of principal	23	38
Other modification of loan terms	8	14
Total	208	240
Total commercial and consumer TDRs	276	297
Total commercial TDRs to total commercial loans	60.00%	70.00%
Total commercial TDRs to total loans	42.00%	48.00%
Total commercial loans	34,782	34,520
Total loans	$ 49,575	$ 50,107

Commercial and consumer TDRs.

No definition available.

Name:	key_CommercialAndConsumerTdrs
Namespace Prefix:	key_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	key_ConcessionTypesForOurCommercialAccruingAndNonaccruingTdrsAbstract
Namespace Prefix:	key_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Financing receivable modifications concessions.

+ References

No definition available.

+ Details

Name:	key_FinancingReceivableModificationsConcessions
Namespace Prefix:	key_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Financing receivable modifications concessions forgiveness of principal.

+ References

No definition available.

+ Details

Name:	key_FinancingReceivableModificationsConcessionsForgivenessOfPrincipal
Namespace Prefix:	key_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Financing receivable modifications concessions interest rate reduction.

+ References

No definition available.

+ Details

Name:	key_FinancingReceivableModificationsConcessionsInterestRateReduction
Namespace Prefix:	key_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Financing receivable modifications concessions other.

+ References

No definition available.

+ Details

Name:	key_FinancingReceivableModificationsConcessionsOther
Namespace Prefix:	key_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Percentage of Commercial TDRs to commercial loans.

+ References

No definition available.

+ Details

Name:	key_PercentageOfCommercialTdrsToCommercialLoans
Namespace Prefix:	key_
Data Type:	us-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage of commercial TDRs to loans.

+ References

No definition available.

+ Details

Name:	key_PercentageOfCommercialTdrsToLoans
Namespace Prefix:	key_
Data Type:	us-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Reflects the sum of the gross carrying amounts of the various categories of unpaid commercial loans and leases receivable, primarily issued to businesses. Includes: (1) commercial and industrial loans, consisting of general purpose loans to entities involved in producing, transporting, or merchandising products sold in the course of commerce; (2) agricultural loans consisting of borrowings used to finance major equipment and machinery purchases and expenses, livestock or crop production (including fisheries), and to supplement working capital needs of an entity engaged in farming operations; (3) mortgage loans secured by a [legal] security interest in real property [commercial building or business real property]; (4) obligation in the form of [promissory] notes, used for the funding of construction projects; (5) interbank and other loans to financial institutions for the purpose of liquidity management on the part of the borrower; (6) draws against credit facilities provided to companies involved in mortgage banking activities (warehousing); (7) amounts lent to businesses engaged in international activities (trade financing); (8) lease financings; and (9) loans to governmental entities.

+ References

+ Details

Name:	us-gaap_LoansAndLeasesReceivableCommercial
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Reflects the aggregate gross carrying amount of all categories of loans and leases held in portfolio, after deducting deferred income, but before deducting the allowance for losses on loans and leases.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Statement of Position (SOP)

-Number 01-6

-Paragraph 13

-Subparagraph e

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Audit and Accounting Guide (AAG)

-Number AAG-DEP

-Chapter 8

-Paragraph 116

-IssueDate 2006-05-01

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher OTS

-Name Federal Regulation (FR)

-Number Title 12

-Chapter V

-Section 563c.102

-Paragraph 8

-Subparagraph e

-Subsection I

+ Details

Name:	us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant