Consolidated Statements of Changes in Shareholders Equity (Unaudited) (Parenthetical) (USD $) In Millions, except Per Share data, unless otherwise specified	6 Months Ended
Jun. 30, 2011 Series B Preferred Stock Retained Earnings	Jun. 30, 2010 Series B Preferred Stock Retained Earnings	Jun. 30, 2011 Accumulated Other Comprehensive Income (Loss)	Jun. 30, 2010 Accumulated Other Comprehensive Income (Loss)	Jun. 30, 2011 Comprehensive Income (Loss)	Jun. 30, 2010 Comprehensive Income (Loss)
Income taxes effect on net unrealized (losses) gains on securities available for sale			$ 61	$ 136	$ 61	$ 136
Income taxes effect on net unrealized (losses) gains on derivative financial instruments			$ 4	$ (39)	$ 4	$ (39)
Cash dividends declared on common shares, per share	$ 0.04	$ 0.02
Cash dividends declared on Preferred Stock, per share/annum	3.875	3.875
Cash dividends accrued on Cumulative Series B Preferred Stock, (% per annum)	5.00%	5.00%

Cash dividends declared during the period on Preferred Stock, per share/annum.

Name:	key_CashDividendsOnSeriesPreferredStockPerShare
Namespace Prefix:	key
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Preferred Stock Dividend Rate Percentage.

+ Details

Name:	key_PreferredStockDividendRatePercentage
Namespace Prefix:	key
Data Type:	us-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Aggregate dividends declared during the period for each share of common stock outstanding.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 04
-Article 3

+ Details

Name:	us-gaap_CommonStockDividendsPerShareDeclared
Namespace Prefix:	us-gaap
Data Type:	us-types:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Tax effect on the change in accumulated gains and losses from derivative instruments designated and qualifying as the effective portion of cash flow hedges. Includes an entity's share of an equity investee's increase (decrease) in deferred hedging gains or losses.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Accounting Research Bulletin (ARB)
-Number 51
-Paragraph 38
-Subparagraph c(3)

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 130
-Paragraph 25

+ Details

Name:	us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodTax
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Tax effect on gross appreciation or the gross loss in value of the total of unsold securities during the period being reported on.

+ References

+ Details

Name:	us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration