CASH AND DUE FROM BANKS AT END OF PERIOD CASH AND DUE FROM BANKS AT BEGINNING OF PERIOD Cash and due from banks Trading account assets Securities available for sale Held-to-maturity securities (fair value: $19, $24 and $25) Held-to-maturity Securities Held-to-maturity securities (fair value: $25, $25 and $29) Held-to-maturity Securities, Total Loans, net of unearned income of $1,641, $1,770 and $1,994 Loans and Leases Receivable, Net of Deferred Income Loans and Leases Receivable, Net of Deferred Income Loans, net of unearned income of $1,995, $2,345 and $2,532 Less: Allowance for loan losses Net loans Loans held for sale Premises and equipment Other intangible assets Corporate-owned life insurance Total assets Accrued income and other assets (including $134 of consolidated LIHTC guaranteed funds VIEs, see Note 7) (a) Other Assets Accrued income and other assets Accrued income and other assets Derivative assets Total deposits Deposits in foreign office - interest-bearing Total interest-bearing Federal funds purchased and securities sold under repurchase agreements Derivative liabilities Total liabilities Other Liabilities Accrued expense and other liabilities ($xxx,xxx,xxx relates to consolidated VIEs, see also Note X) Other Liabilities, Total Accrued expense and other liabilities Long-term debt Bank notes and other short-term borrowings Retained earnings Capital surplus Accumulated other comprehensive income (loss) Key shareholders' equity Total liabilities and equity Noncontrolling interests Operating lease assets Loans held for sale Securities available for sale Held-to-maturity securities Total interest income Loans Deposits Federal funds purchased and securities sold under repurchase agreements Long-term debt Total interest expense NET INTEREST INCOME Provision for loan losses Net interest (expense) income after provision for loan losses Service charges on deposit accounts The aggregate interest income earned from federal funds sold, securities purchased under agreements to resell and interest-bearing deposits due from other financial institutions. Short-term investments income Short-term investments Operating lease income Fees related to letters of credit, loan commitment fees, syndication fees and other nonyield-related loan fees. Letter of Credit and Loan Fees Corporate-owned life insurance income Total noninterest expense Other expense Marketing Equipment Professional fees Computer processing Net occupancy Total noninterest income Net losses (gains) from principal investing Net (losses) gains from principal investing Gain (Loss) on Sale of Securities, Net Net securities losses (gains) Net securities gains (losses) Gain (Loss) on Sale of Securities, Net Net securities (losses) gains Net securities gains (losses) Income derived from investment banking activities, dealer trading and derivatives, foreign exchange income, and other capital markets activities. Investment Banking and Capital Markets Income Fees received from other banking institutions for processing PIN based point of sale transactions. Also includes various ATM-related fees and income. Electronic Banking Fees Represents insurance premiums and commission income earned through the sale of annuity and other insurance products. Insurance Income Expenses related to operating leases such as depreciation expense on leased equipment. Operating Lease Expense Income taxes Net Income (Loss) Attributable to Parent NET INCOME (LOSS) ATTRIBUTABLE TO KEY NET INCOME (LOSS) ATTRIBUTABLE TO KEY Net income (loss) Weighted-average common shares outstanding (000) Provision for loan losses Depreciation and amortization expense Series A Preferred Stock Series B Preferred Stock Increase (Decrease) in Deferred Income Taxes Deferred income taxes Deferred income taxes Deferred income taxes NET CASH PROVIDED BY (USED IN) OPERATING ACTIVITIES Purchases of securities available for sale Proceeds from sales of securities available for sale Proceeds from prepayments and maturities of securities available for sale Purchases of held-to-maturity securities Proceeds from prepayments and maturities of held-to-maturity securities Purchases of other investments Proceeds from sales of other investments Proceeds from prepayments and maturities of other investments NET CASH PROVIDED BY (USED IN) INVESTING ACTIVITIES Proceeds from sales of other real estate owned Proceeds from sales of premises and equipment Purchases of premises and equipment Net increase (decrease) in deposits Net increase (decrease) in deposits Net decrease in short-term borrowings Net proceeds from issuance of long-term debt Payments on long-term debt Tax benefits under recognized compensation cost for stock-based awards Cash dividends paid NET CASH PROVIDED BY (USED IN) FINANCING ACTIVITIES NET INCREASE (DECREASE) IN CASH AND DUE FROM BANKS NET (DECREASE) INCREASE IN CASH AND DUE FROM BANKS Ending Balance Beginning Balance Net unrealized gains (losses) on derivative financial instruments, net of income taxes of ($37) and ($39), respectively Other Comprehensive Income, Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax Net unrealized (losses) gains on derivative financial instruments, net of income taxes of ($37) and $1 respectively Held-to-maturity securities, Fair value Held-to-maturity Securities, Fair Value Held-to-maturity securities, Fair Value Preferred Stock, Par Value Common Shares, Par Value Common Shares, Shares Authorized Common Shares, Shares Issued Treasury Stock, Shares Unearned Income on Loans Reflects the cumulative amount of interest and fees paid by borrowers which have not yet been taken into income in conformity with GAAP. Also reflects the amount of unamortized costs incurred to originate loans and leases, unamortized loan commitments and loan syndication fees, and premiums over or discounts from face amounts of acquired loans that are being amortized into income as an adjustment to yield. Unearned Income Loan Line of Business Results Line of Business Results [Abstract] Securities Securities [Abstract] Capital Securities Issued by Unconsolidated Subsidiaries Capital Securities Issued by Unconsolidated Subsidiaries [Abstract] Fair Value Measurements Fair Value Measurements [Abstract] Fair Value Measurements Derivatives and Hedging Activities Income Taxes Increase (Decrease) in Other Operating Assets and Liabilities, Net Other operating activities, net Other operating activities, net Other operating activities, net Other operating activities, net Increase (Decrease) in Loans Held-for-sale Net decrease (increase) in loans held for sale excluding transfers from continuing operations Increase (Decrease) in Loans Held-for-sale Net increase in loans held for sale Net decrease (increase) in loans held for sale excluding transfers from continuing operations A description of the business trusts that issued corporation-obligated mandatorily redeemable preferred capital securities and related activity for the year-to-date period. Also includes a tabular disclosure of the carrying amount of the capital securities and common stock issued by the trusts, the principal amount of related debentures issued by KeyCorp and purchased by the trusts, and the interest rates and maturities of the capital securities and debentures as of the balance sheet date. Capital Securities Issued by Unconsolidated Subsidiaries Capital Securities Issued by Unconsolidated Subsidiaries Employee Benefits Income taxes effect on net unrealized gains on securities available for sale Income taxes effect on net unrealized (losses) gains on derivative financial instruments Cash dividends declared on common shares, per share Cash dividends declared on Preferred Stock, per share/annum Cash dividends declared during the period on Preferred Stock, per share/annum. Cash dividends declared on Preferred Stock, per share/annum Loans and Loans Held for Sale. Loans and Loans Held for Sale [Abstract] Discloses loans receivable and loans receivable held for sale. Also includes a roll-forward of the allowance for loan losses, a roll-forward for liability for credit losses on lending-related commitments, composition of the net investment in direct financing leases and minimum future lease payments receivables as well as the related allowance. Loans And Loans Held For Sale Loans and Loans Held for Sale Interest paid Income taxes (refunded) paid Loans transferred to portfolio from held for sale Loans transferred to other real estate owned Deposits in domestic offices. Deposits In Domestic Offices [Abstract] Common Stock Warrant. Common Stock Warrant Common Stock Warrant Preferred Stock Common Shares Capital Surplus Retained Earnings Treasury Stock, at Cost Accumulated Other Comprehensive Income (Loss) Comprehensive Income (Loss) Interest paid Line of Business Results [Abstract] Securities [Abstract] Loans and Loans Held for Sale [Abstract] Capital Securities Issued by Unconsolidated Subsidiaries [Abstract] Fair Value Measurements [Abstract] ASSETS LIABILITIES EQUITY Deposits in domestic offices: Common stock warrant Common stock warrant A warrant to purchase common shares to the U.S. Treasury at a fair value of $87 million. Other time deposits Other time deposits The aggregate amount of time deposits, including certificates of deposit of less than $100,000, individual retirement accounts and open accounts. NOW and money market deposit accounts NOW and money market deposit accounts Amount of deposits in interest-bearing accounts that offer many of the same services as checking accounts although transactions may be somewhat more limited. These deposits include those that share some of the characteristics of a money market fund and are insured by the Federal government, also known as money market deposits accounts (MMDAs). Also included are deposits in interest-bearing transaction accounts, that are restricted with regard to ownership and can usually only be held by individuals, nonprofit entities and governments. These deposits, also known as negotiable order of withdrawal (NOW) accounts, differ from money market deposit accounts, as they typically have higher deposit reserve requirements and no limit on the number of checks that can be written. INTEREST INCOME INTEREST EXPENSE NONINTEREST INCOME NONINTEREST EXPENSE OPERATING ACTIVITIES INVESTING ACTIVITIES FINANCING ACTIVITIES Additional disclosures relative to cash flows: Noncash items: Entity Public Float (actual number) Entity Common Stock, Shares Outstanding (actual number) Letter of credit and loan fees Electronic banking fees Insurance income Investment banking and capital markets income (loss) Operating lease expense FDIC assessment FDIC assessment Represents deposit reserve assessments charged by the Federal Deposit Insurance Corporation. Securities Securities This item represents the entire disclosure related to securities which consist of all investments in certain debt and equity securities classified as available-for-sale or held-to-maturity securities. Short-term investments Short term investment Federal funds sold, securities purchased under agreements to resell and interest-bearing deposits due from other financial institutions. Savings deposits Savings deposits The amount of interest bearing deposits with no stated maturity, which may include passbook and statement savings accounts. Certificates of deposit ($100,000 or more) Certificates of deposit The aggregate amount of certificates of deposit of $100,000 or more. Noninterest-bearing Noninterest-bearing The aggregate amount of all noninterest-bearing deposit liabilities held by the entity. Common Stock Values Common shares, $1 par value; authorized 1,400,000,000 shares; issued 584,061,120, 584,061,120 and 491,888,780 shares Common shares, $1 par value; authorized 1,400,000,000 shares; issued 946,348,435, 946,348,435 and 865,070,221 shares Carrying amount of issued common stock that may be calculated differently depending on whether the stock is issued at par value, no par or stated value. Treasury stock, at cost (65,833,721, 67,813,492 and 67,824,373 shares) Treasury Stock Values Treasury stock, at cost (85,487,810, 89,058,634, and 91,818,259 shares) Treasury stock, at cost (67,813,492 and 89,058,634 shares) The cost of common and preferred stock of an entity that has been repurchased by the entity. Treasury stock is issued but not outstanding. This stock has no voting rights and receives no dividends. Preferred Stock, Shares Authorized Preferred Stock Share Authorized Total preferred stock shares authorized for current or future issuance. Trading account assets Trading Account Assets Interest income derived from securities and loans held for trading purposes. Bank notes and other short-term borrowings Other income Other Income Noninterest Other noninterest income that is not separately presented in any other category. Intangible Assets Impairment Intangible assets impairment The amount of impairment loss recognized from the write-down of the carrying amount of an intangible asset (including goodwill) to fair value. Net decrease (increase) in short-term investments Net decrease (increase) in short-term investments Net decrease in short term investments The net cash inflow and outflow of federal funds sold, securities purchased under agreements to resell and interest-bearing deposits due from other financial institutions. Net decrease increase in loans excluding acquisitions sales and transfers Net decrease (increase) in loans, excluding acquisitions, sales and transfers Net decrease (increase) in loans, excluding acquisitions, sales and transfers The net change in the total loans, excluding acquisitions, sales and transfers. Net pension and postretirement benefit costs, net of income taxes Depreciation and amortization expense Depreciation, Amortization and Accretion, Net Line of Business Results Employee Benefits Income Taxes Derivatives and Hedging Activities Fair Value Measurements Cash and due from banks Cash and Due from Banks Trading account assets Securities available for sale Available-for-sale Securities Less: Allowance for loan losses Loans and Leases Receivable, Allowance, Beginning Balance Loans and Leases Receivable, Allowance, Ending Balance Loans held for sale Loans Receivable Held-for-sale, Net, Beginning Balance Loans Receivable Held-for-sale, Net, Ending Balance Loans Receivable Held-for-sale, Net Premises and equipment Property, Plant and Equipment, Net, Beginning Balance Property, Plant and Equipment, Net, Ending Balance Property, Plant and Equipment, Net Operating lease assets Goodwill Goodwill, Beginning Balance Goodwill, Ending Balance Other intangible assets Intangible Assets, Net (Excluding Goodwill) Corporate-owned life insurance Derivative assets Derivative Assets, Total Total interest-bearing Deposits in foreign office - interest-bearing Deposits in foreign office - interest-bearing Federal funds purchased and securities sold under repurchase agreements Federal Funds Purchased and Securities Sold under Agreements to Repurchase Bank notes and other short-term borrowings Short-term Borrowings Derivative liabilities Derivative Liabilities, Total Long-term debt Long-term Debt Capital surplus Additional Paid in Capital, Beginning Balance Additional Paid in Capital, Ending Balance Additional Paid in Capital Retained earnings Retained Earnings (Accumulated Deficit), Beginning Balance Retained Earnings (Accumulated Deficit), Ending Balance Retained Earnings (Accumulated Deficit) Accumulated other comprehensive income Accumulated Other Comprehensive Income (Loss), Net of Tax, Beginning Balance Accumulated Other Comprehensive Income (Loss), Net of Tax, Ending Balance Accumulated Other Comprehensive Income (Loss), Net of Tax Noncontrolling interest Minority Interest, Beginning Balance Minority Interest, Ending Balance Preferred Stock, Par Value Common Shares, Par Value Common Shares, Shares Authorized Common Shares, Shares Issued Common Stock, Shares, Issued, Total Loans Interest and Fee Income, Loans and Leases Held-in-portfolio Loans held for sale Interest and Fee Income, Loans and Leases Held-for-sale Securities available for sale Held-to-maturity securities Deposits Interest Expense, Deposits Federal funds purchased and securities sold under repurchase agreements Interest Expense, Federal Funds Purchased and Securities Sold under Agreements to Repurchase Bank notes and other short-term borrowings Interest Expense, Short-term Borrowings Excluding Federal Funds and Securities Sold under Agreements to Repurchase Long-term debt Interest Expense, Long-term Debt Provision for loan losses Service charges on deposit accounts Operating lease income Operating Leases, Income Statement, Lease Revenue, Total Corporate-owned life insurance income Net gains (losses) from principal investing Net occupancy Computer processing Communications and Information Technology Professional fees Equipment Marketing Marketing and Advertising Expense Other expense Income taxes Income Tax Expense (Benefit) Cash dividends declared per common share Weighted-average common shares outstanding (000) Key shareholders' equity Net pension and postretirement benefit costs, net of income taxes Other Comprehensive Income, Defined Benefit Plans Adjustment, Net of Tax, Period Increase (Decrease) Ending Balance Income taxes effect on net unrealized (losses) gains on securities available for sale Income taxes effect on net unrealized (losses) gains on derivative financial instruments Purchases of securities available for sale Payments to Acquire Available-for-sale Securities Proceeds from sales of securities available for sale Proceeds from Sale of Available-for-sale Securities Proceeds from prepayments and maturities of securities available for sale Purchases of held-to-maturity securities Proceeds from prepayments and maturities of held-to-maturity securities Purchases of other investments Proceeds from sales of other investments Proceeds from prepayments and maturities of other investments Purchases of premises and equipment Payments to Acquire Property, Plant, and Equipment Proceeds from sales of premises and equipment Proceeds from Sale of Property, Plant, and Equipment Proceeds from sales of other real estate owned Increase (Decrease) in Deposits Net increase (decrease) in short-term borrowings Proceeds from (Repayments of) Short-term Debt Net proceeds from issuance of long-term debt Proceeds from Issuance of Long-term Debt Payments on long-term debt Repayments of Long-term Debt Tax benefits over (under) recognized compensation cost for stock-based awards Cash dividends paid Payments of Dividends Interest paid Income taxes paid (refunded) Income Taxes Paid, Net Loans transferred to portfolio from held for sale Loans transferred to other real estate owned NOW and money market deposit accounts Short Term Investments Income FDIC assessment Common Stock Warrant Common Stock, Dividends, Per Share, Declared Other income Other expense Premises and equipment Preferred stock Noncontrolling interest Total equity Preferred Stock, Liquidation Preference Net Income (Loss) Attributable to Noncontrolling Interest Less: Net income (loss) attributable to noncontrolling interests Less: Net income (loss) attributable to noncontrolling interests Net income (loss) attributable to noncontrolling interests Net income (loss) Earnings Per Share, Basic, Total Net (loss) income attributable to Key Earnings Per Share, Diluted, Total Net (loss) income attributable to Key - assuming dilution Net income (loss) Comprehensive Income, Net of Tax, Including Portion Attributable to Noncontrolling Interest Total comprehensive loss Total comprehensive income (loss) Cash dividends declared on common shares ($.0725 per share) and ($.02 per share) respectively Cash dividends declared on preferred stock Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders Net distribution from noncontrolling interests Net distribution to noncontrolling interests Noncontrolling Interest, Increase from Stock Issuance or Sale of Parent Equity Interest Net contribution to noncontrolling interests Other investments Other investments Interest income earned on other investments not otherwise specified in the taxonomy that generally will be realized in a short period of time, usually less than one year or the normal operating cycle, whichever is longer. Earnings Per Common Share Beginning Balance Ending Balance Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest Less: Allowance for loan losses Loans and Leases Receivable, Allowance Net loans Loans and Leases Receivable, Net Reported Amount Other time deposits Interest-bearing Deposit Liabilities, Foreign Total liabilities Liabilities Accumulated Other Comprehensive Income (Loss), Net of Tax Stockholders' Equity Attributable to Noncontrolling Interest Preferred Stock, Value, Issued, Total Preferred Stock, Value, Issued, Beginning Balance Preferred Stock, Value, Issued, Ending Balance Preferred Stock, Value, Issued NET CASH PROVIDED BY (USED IN) OPERATING ACTIVITIES Net Cash Provided by (Used in) Operating Activities Proceeds from sales of other real estate owned Proceeds from Sale of Wholly Owned Real Estate and Real Estate Acquired in Settlement of Loans NET CASH PROVIDED BY (USED IN) INVESTING ACTIVITIES Net Cash Provided by (Used in) Investing Activities Payments of Dividends Total interest income Interest and Dividend Income, Operating NET INTEREST INCOME Interest Income (Expense), Net Net interest income (expense) after provision for loan losses Interest Income (Expense), after Provision for Loan Loss Total noninterest income Noninterest Income Total noninterest expense Noninterest Expense NET INCOME (LOSS) Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Common Stock, Dividends, Per Share, Declared Cash and Due From Banks Dividends, Preferred Stock, Cash Cash and Cash Equivalents, Period Increase (Decrease) Total deposits Deposits Stockholders' Equity Attributable to Parent Cash Dividends On Series Preferred Stock Per Share Common Stock, Shares, Outstanding Ending Balance, Shares Beginning Balance, Shares Proceeds from sale/redemption of Visa Inc. shares Proceeds from sale/redemption of Visa Inc. shares Proceeds from the sale or redemption of Visa Inc. shares. Noninterest Bearing Proceeds From Sale Or Redemption Of Visa Inc Securities Securities [Text Block] Loans And Loans Held For Sale [Text Block] Capital Securities Issued By Unconsolidated Subsidiaries [Text Block] Trust and investment services income Trust and Investment Services Income Brokerage commissions and fee income, personal asset management and custody fees, and institutional asset management and custody fees. Net income (loss) attributable to Key common shareholders Net Income (Loss) Available to Common Stockholders, Basic, Total Net Income (Loss) Available to Common Stockholders, Basic Shareholders' Equity Stockholders' Equity Note Disclosure [Text Block] Loans transferred to other real estate owned Transfer Other Real Estate Now And Money Market Deposit Accounts Other Investments Interest FDIC Assessment Foreign currency translation adjustments Other Comprehensive Income, Foreign Currency Transaction and Translation Adjustment, Net of Tax, Total Other Comprehensive Income, Foreign Currency Transaction and Translation Adjustment, Net of Tax Cash dividends paid Payments on long-term debt Repayments of Long-term Debt Purchases of premises and equipment Payments to Acquire Property, Plant, and Equipment Purchases of other investments Payments to Acquire Other Investments Purchases of held-to-maturity securities Payments to Acquire Held-to-maturity Securities Purchases of securities available for sale Payments to Acquire Available-for-sale Securities Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Principal Investment Gains (Losses) Net Cash Provided by (Used in) Financing Activities Loans transferred to held for sale from portfolio Transfer of Portfolio Loans and Leases to Held-for-sale INCOME (LOSS) FROM CONTINUING OPERATIONS BEFORE INCOME TAXES Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Cumulative Effects of Changes in Accounting Principles, Noncontrolling Interest, Total Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Cumulative Effects of Changes in Accounting Principles, Noncontrolling Interest Income (loss) from discontinued operations, net of taxes, of ($17), ($8), ($15) and ($14) (see Note 16) Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest Income (loss) from continuing operations attributable to Key common shareholders Loss From Continuing Operations Attributable To Key Common Shareholders Loss from continuing operations after adjustments for dividends on preferred stock (declared in the period) and/or cumulative preferred stock (accumulated for the period). Per common share: Earnings Per Share, Basic [Abstract] Income (Loss) from Discontinued Operations, Net of Tax, Per Basic Share Income (Loss) from Discontinued Operations, Net of Tax, Per Outstanding Share, Total Income (loss) from discontinued operations, net of taxes Net income (loss) attributable to Key common shareholders Earnings Per Share, Basic Per common share - assuming dilution: Earnings Per Share, Diluted [Abstract] Income (Loss) from Discontinued Operations, Net of Tax, Per Diluted Share Income (Loss) from Discontinued Operations, Net of Tax, Per Diluted Share, Total Income (loss) from discontinued operations, net of taxes Net income (loss) attributable to Key common shareholders Earnings Per Share, Diluted Weighted Average Number of Shares Outstanding, Basic, Total Weighted Average Number of Shares Outstanding, Basic Net unrealized gains (losses) on securities available for sale, net of income taxes of ($23) and $136, respectively Other Comprehensive Income Unrealized Holding Gains Losses On Securities Arising During Period Net Of Tax Appreciation or loss in value (net of reclassification adjustments) of the total of unsold securities during the period being reported on, net of tax. Reclassification adjustments include: (1) the unrealized holding gain or loss, net of tax, at the date of the transfer for a debt security from the held-to-maturity category transferred into the available-for-sale category. Also includes the unrealized gain or loss at the date of transfer for a debt security from the available-for-sale category transferred into the held-to-maturity category; (2) the unrealized gains or losses realized upon the sale of securities, after tax; and (3) the unrealized gains or losses realized upon the write-down of securities, after tax. Deferred compensation Deferred Compensation The value of deferred stock compensation and dividends declared on deferred stock compensation. Dividends, Common Stock, Cash Entity Registrant Name Entity Central Index Key Document Type Document Period End Date Amendment Flag Current Fiscal Year End Date Entity Well-known Seasoned Issuer Entity Voluntary Filers Entity Current Reporting Status Entity Filer Category Entity Public Float Entity Common Stock, Shares Outstanding Statement [Table] Class of Stock [Axis] Class of Stock [Domain] Statement [Line Items] Assets [Abstract] Trading Securities Available-for-sale Securities Loans Receivable Held-for-sale, Net Property, Plant and Equipment, Net Property Subject to or Available for Operating Lease, Gross Goodwill Intangible Assets, Net (Excluding Goodwill) Bank Owned Life Insurance Derivative Assets Assets Liabilities [Abstract] Interest-bearing Deposit Liabilities, Domestic Federal Funds Purchased and Securities Sold under Agreements to Repurchase Short-term Borrowings Derivative Liabilities Long-term Debt Stockholders' Equity Attributable to Parent [Abstract] Additional Paid in Capital Retained Earnings (Accumulated Deficit) Liabilities and Stockholders' Equity Preferred Stock, Par or Stated Value Per Share Preferred Stock, Liquidation Preference Per Share Preferred Stock, Shares Issued, Total Preferred Stock, Shares Issued Common Stock, Par or Stated Value Per Share Common Stock, Shares Authorized Common Stock, Shares, Issued Treasury Stock, Shares Interest and Dividend Income, Operating [Abstract] Interest and Fee Income, Loans and Leases Held-in-portfolio Interest and Fee Income, Loans and Leases Held-for-sale Interest and Dividend Income, Securities, Available-for-sale Interest and Dividend Income, Securities, Held-to-maturity Interest Expense [Abstract] Interest Expense, Deposits Interest Expense, Federal Funds Purchased and Securities Sold under Agreements to Repurchase Interest Expense, Short-term Borrowings Excluding Federal Funds and Securities Sold under Agreements to Repurchase Interest Expense, Long-term Debt Interest Expense Provision for Loan and Lease Losses Noninterest Income [Abstract] Fees and Commissions, Depositor Accounts Operating Leases, Income Statement, Lease Revenue Bank Owned Life Insurance Income Noninterest Expense [Abstract] Occupancy, Net Communications and Information Technology Professional Fees Equipment Expense Marketing and Advertising Expense Other Noninterest Expense Income Tax Expense (Benefit) Other Comprehensive Income, Defined Benefit Plans Adjustment, Net of Tax Statement, Equity Components [Axis] Equity Component [Domain] Other Comprehensive Income, Unrealized Holding Gain (Loss) on Securities Arising During Period, Tax Other Comprehensive Income, Unrealized Gain (Loss) on Derivatives Arising During Period, Tax Net Cash Provided by (Used in) Operating Activities [Abstract] Depreciation, Amortization and Accretion, Net Net Cash Provided by (Used in) Investing Activities [Abstract] Proceeds from Sale of Available-for-sale Securities Proceeds from Maturities, Prepayments and Calls of Available-for-sale Securities Proceeds from Maturities, Prepayments and Calls of Held-to-maturity Securities Proceeds from Sale of Other Investments Proceeds from Maturities, Prepayments and Calls of Other Investments Proceeds from Sale of Property, Plant, and Equipment Net Cash Provided by (Used in) Financing Activities [Abstract] Increase (Decrease) in Deposits Proceeds from (Repayments of) Short-term Debt Proceeds from Issuance of Long-term Debt Excess Tax Benefit from Share-based Compensation, Financing Activities Supplemental Cash Flow Information [Abstract] Interest Paid, Net Income Taxes Paid, Net Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract] Transfer of Loans Held-for-sale to Portfolio Loans Earnings Per Share [Text Block] Segment Reporting Disclosure [Text Block] Pension and Other Postretirement Benefits Disclosure [Text Block] Income Tax Disclosure [Text Block] Derivative Instruments and Hedging Activities Disclosure [Text Block] Fair Value Disclosures [Text Block] Preferred stock, $1 par value, authorized 25,000,000 shares: Preferred Stock, Number of Shares, Par Value and Other Disclosures [Abstract] Weighted-average common shares and potential common shares outstanding (000) Weighted Average Number of Shares Outstanding, Diluted, Total Weighted Average Number of Shares Outstanding, Diluted Income (loss) from continuing operations attributable to Key common shareholders Income (Loss) From Continuing Operations Attributable To Key Commons Shareholders Per Diluted Share The amount of income (loss) from continuing operations after adjustments for dividends on preferred stock (declared in the period) and/or cumulative preferred stock (accumulated for the period) available to each share of common stock outstanding during the reporting period and each share that would have been outstanding assuming the issuance of common shares for all dilutive potential common shares outstanding during the reporting period. Income (loss) from continuing operations attributable to Key common shareholders Income (Loss) From Continuing Operations Attributable To Commons Shareholders Per Basic Share The amount of income (loss) from continuing operations after adjustments for dividends on preferred stock (declared in the period) and/or cumulative preferred stock (accumulated for the period) per each share of common stock outstanding during the reporting period. Net tax effect on loss from discontinued operations Net Tax Effect On Income Loss From Discontinued Operations Net tax effect on income (loss) from discontinued operations. Preferred Stock, Shares Issued, Total INCOME (LOSS) FROM CONTINUING OPERATIONS Income (Loss) From Continuing Operation This element represents the income or loss from continuing operations attributable to the reporting entity which may also be defined as revenue less expenses and taxes from ongoing operations before extraordinary items and cumulative effects of changes in accounting principles, and before deduction of those portions of income or loss from continuing operations that are allocable to noncontrolling interests, if any. Gains on leased equipment Gains Losses On Leased Equipment Gains on leased equipment. Provision (credit) for losses on lending-related commitments Provision (Credit) for Losses on Lending-Related Commitments Represents portion of current operating income set aside to provide an adequate reserve against losses incurred from lending-related commitments. Cash dividends accrued on Cumulative Series B Preferred Stock, (% per annum) Preferred Stock, Dividend Rate Preferred Stock, Dividend Rate, Percentage or Per-Dollar-Amount Gain from sale/redemption of Visa Inc. shares Gain From Sale Or Redemption Of Securities Gain from sale or redemption of Visa Inc. shares Gain from sale/redemption of Visa Inc. shares Noncontroling Interests Noncontrolling Interests Stock Issued During Period, Value, Share-based Compensation Common shares reissued - Stock options and other employee benefit plans Common shares reissued for stock options and other employee benefit plans Common shares reissued for stock options and other employee benefit plans, Shares (000) Stock Issued During Period, Shares, Share-based Compensation Common shares reissued - Stock options and other employee benefit plans, Shares (000) Amortization of discount on Series B Preferred Stock Increase in Carrying Amount of Redeemable Preferred Stock Discontinued assets (including $3,285 of consolidated education loan securitization trusts VIEs at fair value, see Note 7) (a) Assets of Disposal Group, Including Discontinued Operation Discontinued liabilities (including $3,135 of consolidated education loan securitization trusts VIEs at fair value, see Note 7) (a) Liabilities of Disposal Group, Including Discontinued Operation Earnings Per Common Share [Abstract] Earnings Per Common Share [Abstract] Shareholders' Equity [Abstract] Employee Benefits [Abstract] Derivatives and Hedging Activities [Abstract] Parent [Member] Income Taxes [Abstract] Consolidated Balance Sheets [Abstract] Consolidated Statements of Income [Abstract] Consolidated Statements of Changes in Shareholders Equity [Abstract] Consolidated Statements of Cash Flows [Abstract] Common Stock Warrant Cumulative Effect of Initial Adoption of New Accounting Principle Cumulative effect adjustment to beginning balance of Retained Earnings Other comprehensive income (loss): Basis of Presentation [Abstract] Commitments, Contingent Liabilities and Guarantees [Abstract] Commitments, Contingent Liabilities and Guarantees [Abstract] Commitments, Contingent Liabilities and Guarantees. Commitments, Contingent Liabilities and Guarantees Commitments Contingent Liabilities And Guarantees [Text Block] Disclosure of obligations under noncancelable leases, commitments to extend credit or funding, legal proceedings, guarantees and other off-balance sheet risk. Nonperforming Assets and Past Due Loans From Continuing Operations [Abstract] Nonperforming Assets and Past Due Loans From Continuing Operations. Nonperforming Assets and Past Due Loans From Continuing Operations Nonperforming Assets And Past Due Loans From Continuing Operations [Text Block] Tabular disclosure and description of total nonperforming assets and past due loans. Personnel Labor and Related Expense, Total Labor and Related Expense OREO expense, net Gains (Losses) on Sales of Other Real Estate Gains on leased equipment Variable Interest Entities [Abstract] Variable Interest Entities Abstract. Variable Interest Entities Schedule of Variable Interest Entities [Text Block] Mortgage Servicing Assets [Abstract] Transfers and Servicing of Financial Assets [Text Block] Mortgage Servicing Assets OREO expense, net Preferred Stock, Shares Outstanding Ending Balance, Shares Beginning Balance, Shares Accrued income and other assets of Consolidated Vies Accrued income and other assets of consolidated VIEs Accrued income and other assets of Consolidated VIEs. Discontinued assets of consolidated VIEs at fair value. Discontinued assets of consolidated Vies at fair value Discontinued assets of consolidated VIEs at fair value Document and Entity Information. Document and Entity Information [Abstract] Document Fiscal Year Focus Document Fiscal Period Focus Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Basis of Presentation Discontinued Operations [Abstract] Disposal Groups, Including Discontinued Operations, Disclosure [Text Block] Discontinued Operations Consolidated Education loan securitization trusts VIE's at fair value Consolidated Education loan securitization trusts VIE'S at fair value. Consolidated Education loan securitization trusts Vies at fair value Proceeds From Loan Sales Proceeds from loan sales The cash inflow from loan sales. Gain Related To Exchange Of Common Shares For Capital Securities Gain related to exchange of common shares for capital securities Gain related to exchange of common shares for capital securities Gain Related to Exchange of Common Shares for Capital Securities. Provision For Losses On Low Income Housing Tax Credit Guaranteed Funds Provision for losses on LIHTC guaranteed funds Provision For Losses on Low Income Housing Tax Credit Guaranteed Funds. Net Proceeds From Issuance Of Common Shares And Preferred Stock Net proceeds from issuance of common shares and preferred stock Net Proceeds from Issuance of Common Shares and Preferred Stock. Gain From Sale Of Company Claim Associated With Other Company Gain from sale of Key's claim associated with the Lehman Gain from Sale of Company Claim Associated With Other Company. Stock Issued During Period, Shares, New Issues Common shares issued, Shares Stock Issued During Period, Value, New Issues Common shares issued Common Shares Exchanged For Series A Preferred Stock Common shares exchanged for Series A Preferred Stock Common Shares Exchanged for Series A Preferred Stock. Common Shares Exchanged For Series A Preferred Stocks Common shares exchanged for Series A Preferred Stock, Shares Common Shares Exchanged For Series A Preferred Stocks. Common Shares Exchanged For Capital Securities Common shares exchanged for capital securities Common Shares Exchanged For Capital Securities. Common Share Exchanged For Capital Securities Common shares exchanged for capital securities, Shares Common Shares Exchanged For Capital Securities. Gain (Loss) on Sales of Loans, Net Net losses (gains) from loan sales Gain (Loss) on Sales of Loans, Net, Total Net gains (losses) from loan sales Other Short-term Investments Other investments Increase (Decrease) in Trading Securities Net decrease (increase) in trading account assets Increase (Decrease) in Trading Securities, Total