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Equity Activity (Reclassification and Taxes Related Tables) (Details 2) (USD $)
In Millions, unless otherwise specified
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Other comprehensive income/(loss), before tax      
Foreign currency translation adjustments, before tax $ (1,636)us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentBeforeTax $ (1,335)us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentBeforeTax $ (44)us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentBeforeTax
Net changes related to available-for-sale securities, before tax      
Unrealized gains/(losses) arising during the period, before tax (29)us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax (4)us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax 8us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax
Reclassification of (gains)/losses to other (income) and expense, before tax 5us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax (8)us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax (42)us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax
Subsequent changes in previously impaired securities arising during the period, before tax 0ibm_OtherComprehensiveIncomeAvailableForSaleSecuritiesSubsequentChangesInPreviouslyImpairedSecuritiesArisingDuringPeriodBeforeTax 4ibm_OtherComprehensiveIncomeAvailableForSaleSecuritiesSubsequentChangesInPreviouslyImpairedSecuritiesArisingDuringPeriodBeforeTax 20ibm_OtherComprehensiveIncomeAvailableForSaleSecuritiesSubsequentChangesInPreviouslyImpairedSecuritiesArisingDuringPeriodBeforeTax
Total net changes related to available-for-sale securities, before tax (24)us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentBeforeTax (8)us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentBeforeTax (14)us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentBeforeTax
Unrealized gains/(losses) on cash flow hedges, before tax      
Unrealized gains/(losses) arising during the period, before tax 958us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax 43us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax 32us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax
Reclassification of (gains)/losses to net income, before tax (97)us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax (166)us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax (253)us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax
Total unrealized gains/(losses) on cash flow hedges, before tax 861us-gaap_OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesBeforeTax (123)us-gaap_OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesBeforeTax (220)us-gaap_OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesBeforeTax
Retirement-related benefit plans, before tax      
Prior service costs/(credits), before tax 1us-gaap_OtherComprehensiveIncomeDefinedBenefitPlanNetPriorServiceCostCreditArisingDuringPeriodBeforeTax 16us-gaap_OtherComprehensiveIncomeDefinedBenefitPlanNetPriorServiceCostCreditArisingDuringPeriodBeforeTax  
Net (losses)/gains arising during the period, before tax (9,799)us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansNetUnamortizedGainLossArisingDuringPeriodBeforeTax 5,369us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansNetUnamortizedGainLossArisingDuringPeriodBeforeTax (7,489)us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansNetUnamortizedGainLossArisingDuringPeriodBeforeTax
Curtailments and settlements, before tax 24us-gaap_OtherComprehensiveIncomeLossFinalizationOfPensionAndNonPensionPostretirementPlanValuationBeforeTax (3)us-gaap_OtherComprehensiveIncomeLossFinalizationOfPensionAndNonPensionPostretirementPlanValuationBeforeTax (2)us-gaap_OtherComprehensiveIncomeLossFinalizationOfPensionAndNonPensionPostretirementPlanValuationBeforeTax
Amortization of prior service (credits)/costs, before tax (114)us-gaap_OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditBeforeTax (114)us-gaap_OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditBeforeTax (148)us-gaap_OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditBeforeTax
Amortization of net (gains)/losses, before tax 2,531us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax 3,499us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax 2,457us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax
Total retirement-related benefit plans, before tax (7,357)us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax 8,767us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax (5,182)us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax
Other Comprehensive Income (Loss), before Tax (8,156)us-gaap_OtherComprehensiveIncomeLossBeforeTax 7,301us-gaap_OtherComprehensiveIncomeLossBeforeTax (5,460)us-gaap_OtherComprehensiveIncomeLossBeforeTax
Other comprehensive income/(loss), tax      
Foreign currency translation adjustments, tax (438)us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentTax (66)us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentTax 10us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentTax
Net changes related to available-for-sale securities, tax      
Unrealized gains/(losses) arising during the period, tax 11us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax 2us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax (4)us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax
Subsequent changes in previously impaired securities arising during the period, tax 0ibm_OtherComprehensiveIncomeAvailableForSaleSecuritiesSubsequentChangesInPreviouslyImpairedSecuritiesArisingDuringPeriodTax (1)ibm_OtherComprehensiveIncomeAvailableForSaleSecuritiesSubsequentChangesInPreviouslyImpairedSecuritiesArisingDuringPeriodTax (8)ibm_OtherComprehensiveIncomeAvailableForSaleSecuritiesSubsequentChangesInPreviouslyImpairedSecuritiesArisingDuringPeriodTax
Total net changes related to available-for-sale securities, tax 9us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesTax 3us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesTax 5us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesTax
Unrealized gains/(losses) on cash flow hedges, tax      
Unrealized gains/(losses) arising during the period, tax (341)us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodTax (15)us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodTax (27)us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodTax
Total unrealized gains/(losses) on cash flow hedges, tax (304)us-gaap_OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesTax 47us-gaap_OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesTax 59us-gaap_OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesTax
Retirement-related benefit plans, tax      
Prior service costs/(credits), tax 0us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansBenefitPlanImprovementTaxEffect [1] 0us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansBenefitPlanImprovementTaxEffect [1]  
Net (losses)/gains arising during the period, tax 3,433us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodTax [1] (1,974)us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodTax [1] 2,327us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodTax [1]
Curtailments and settlements, tax (7)us-gaap_OtherComprehensiveIncomeFinalizationOfPensionAndNonPensionPostretirementPlanValuationTax [1] 1us-gaap_OtherComprehensiveIncomeFinalizationOfPensionAndNonPensionPostretirementPlanValuationTax [1] 0us-gaap_OtherComprehensiveIncomeFinalizationOfPensionAndNonPensionPostretirementPlanValuationTax [1]
Amortization of prior service (credits)/costs, tax 41us-gaap_OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditTax [1] 40us-gaap_OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditTax [1] 59us-gaap_OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditTax [1]
Amortization of net (gains)/losses, tax (852)us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossTax [1] (1,195)us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossTax [1] (874)us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossTax [1]
Total retirement-related benefit plans, tax 2,615us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax [1] (3,128)us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax [1] 1,513us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax [1]
Other comprehensive income/(loss), tax 1,883us-gaap_OtherComprehensiveIncomeLossTax (3,144)us-gaap_OtherComprehensiveIncomeLossTax 1,587us-gaap_OtherComprehensiveIncomeLossTax
Other comprehensive income/(loss), net of tax      
Foreign currency translation adjustments, net of tax (2,074)us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax (1,401)us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax (34)us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax
Net changes related to available-for-sale securities, net of tax      
Unrealized gains/(losses) arising during the period, net of tax (18)us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax (3)us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax 4us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax
Reclassification of (gains)/losses to other (income) and expense, net of tax 3us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax (5)us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax (25)us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax
Subsequent changes in previously impaired securities arising during the period, net of tax 0ibm_OtherComprehensiveIncomeAvailableForSaleSecuritiesSubsequentChangesInPreviouslyImpairedSecuritiesArisingDuringPeriodNet 3ibm_OtherComprehensiveIncomeAvailableForSaleSecuritiesSubsequentChangesInPreviouslyImpairedSecuritiesArisingDuringPeriodNet 12ibm_OtherComprehensiveIncomeAvailableForSaleSecuritiesSubsequentChangesInPreviouslyImpairedSecuritiesArisingDuringPeriodNet
Total net changes related to available-for-sale securities, net of tax (15)us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax (5)us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax (9)us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax
Unrealized gains/(losses) on cash flow hedges, net of tax      
Unrealized gains/(losses) arising during the period, net of tax 618us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodNetOfTax 28us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodNetOfTax 5us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodNetOfTax
Total unrealized gains/(losses) on cash flow hedges, net of tax 557us-gaap_OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax (76)us-gaap_OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax (161)us-gaap_OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax
Retirement-related benefit plans, net of tax      
Prior service costs/(credits), net of tax 1us-gaap_OtherComprehensiveIncomeDefinedBenefitPlanNetPriorServiceCostsCreditArisingDuringPeriodNetOfTax [1] 16us-gaap_OtherComprehensiveIncomeDefinedBenefitPlanNetPriorServiceCostsCreditArisingDuringPeriodNetOfTax [1]  
Net (losses)/gains arising during the period, net of tax (6,366)us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodNetOfTax [1] 3,395us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodNetOfTax [1] (5,162)us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodNetOfTax [1]
Curtailments and settlements, net of tax 17us-gaap_OtherComprehensiveIncomeLossFinalizationOfPensionAndNonPensionPostretirementPlanValuationNetOfTax [1] (2)us-gaap_OtherComprehensiveIncomeLossFinalizationOfPensionAndNonPensionPostretirementPlanValuationNetOfTax [1] (2)us-gaap_OtherComprehensiveIncomeLossFinalizationOfPensionAndNonPensionPostretirementPlanValuationNetOfTax [1]
Amortization of prior service (credits)/costs, net of tax (73)us-gaap_OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditNetOfTax [1] (75)us-gaap_OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditNetOfTax [1] (89)us-gaap_OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditNetOfTax [1]
Amortization of net (gains)/losses, net of tax 1,678us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax [1] 2,304us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax [1] 1,583us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax [1]
Total retirement-related benefit plans, net of tax (4,742)us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax [1] 5,639us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax [1] (3,669)us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax [1]
Other comprehensive income/(loss) (Note L) (6,274)us-gaap_OtherComprehensiveIncomeLossNetOfTax 4,157us-gaap_OtherComprehensiveIncomeLossNetOfTax (3,874)us-gaap_OtherComprehensiveIncomeLossNetOfTax
Cost of sales      
Unrealized gains/(losses) on cash flow hedges, before tax      
Reclassification of (gains)/losses to net income, before tax 15us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_CostOfSalesMember		 34us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_CostOfSalesMember		 (7)us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_CostOfSalesMember
Unrealized gains/(losses) on cash flow hedges, tax      
Reclassification of (gains)/losses to net income, tax (7)us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesTax
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_CostOfSalesMember		 (14)us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesTax
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_CostOfSalesMember		 (6)us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesTax
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_CostOfSalesMember
Unrealized gains/(losses) on cash flow hedges, net of tax      
Reclassification of (gains)/losses to net income, net of tax 9us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesNetOfTax
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_CostOfSalesMember		 21us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesNetOfTax
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_CostOfSalesMember		 (13)us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesNetOfTax
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_CostOfSalesMember
SG&A expense      
Unrealized gains/(losses) on cash flow hedges, before tax      
Reclassification of (gains)/losses to net income, before tax (15)us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_SellingGeneralAndAdministrativeExpensesMember		 (39)us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_SellingGeneralAndAdministrativeExpensesMember		 (16)us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_SellingGeneralAndAdministrativeExpensesMember
Unrealized gains/(losses) on cash flow hedges, tax      
Reclassification of (gains)/losses to net income, tax 6us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesTax
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_SellingGeneralAndAdministrativeExpensesMember		 14us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesTax
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_SellingGeneralAndAdministrativeExpensesMember		 4us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesTax
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_SellingGeneralAndAdministrativeExpensesMember
Unrealized gains/(losses) on cash flow hedges, net of tax      
Reclassification of (gains)/losses to net income, net of tax (9)us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesNetOfTax
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_SellingGeneralAndAdministrativeExpensesMember		 (25)us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesNetOfTax
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_SellingGeneralAndAdministrativeExpensesMember		 (12)us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesNetOfTax
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_SellingGeneralAndAdministrativeExpensesMember
Other (income) and expense      
Net changes related to available-for-sale securities, before tax      
Reclassification of (gains)/losses to other (income) and expense, before tax 5us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax
/ us-gaap_IncomeStatementLocationAxis
= ibm_OtherIncomeExpenseMember		 (8)us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax
/ us-gaap_IncomeStatementLocationAxis
= ibm_OtherIncomeExpenseMember		 (42)us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax
/ us-gaap_IncomeStatementLocationAxis
= ibm_OtherIncomeExpenseMember
Unrealized gains/(losses) on cash flow hedges, before tax      
Reclassification of (gains)/losses to net income, before tax (98)us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax
/ us-gaap_IncomeStatementLocationAxis
= ibm_OtherIncomeExpenseMember		 (162)us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax
/ us-gaap_IncomeStatementLocationAxis
= ibm_OtherIncomeExpenseMember		 (237)us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax
/ us-gaap_IncomeStatementLocationAxis
= ibm_OtherIncomeExpenseMember
Net changes related to available-for-sale securities, tax      
Reclassification of (gains)/losses to other (income) and expense, tax (2)us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesTax
/ us-gaap_IncomeStatementLocationAxis
= ibm_OtherIncomeExpenseMember		 2us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesTax
/ us-gaap_IncomeStatementLocationAxis
= ibm_OtherIncomeExpenseMember		 17us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesTax
/ us-gaap_IncomeStatementLocationAxis
= ibm_OtherIncomeExpenseMember
Unrealized gains/(losses) on cash flow hedges, tax      
Reclassification of (gains)/losses to net income, tax 38us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesTax
/ us-gaap_IncomeStatementLocationAxis
= ibm_OtherIncomeExpenseMember		 62us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesTax
/ us-gaap_IncomeStatementLocationAxis
= ibm_OtherIncomeExpenseMember		 91us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesTax
/ us-gaap_IncomeStatementLocationAxis
= ibm_OtherIncomeExpenseMember
Net changes related to available-for-sale securities, net of tax      
Reclassification of (gains)/losses to other (income) and expense, net of tax 3us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax
/ us-gaap_IncomeStatementLocationAxis
= ibm_OtherIncomeExpenseMember		 (5)us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax
/ us-gaap_IncomeStatementLocationAxis
= ibm_OtherIncomeExpenseMember		 (25)us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax
/ us-gaap_IncomeStatementLocationAxis
= ibm_OtherIncomeExpenseMember
Unrealized gains/(losses) on cash flow hedges, net of tax      
Reclassification of (gains)/losses to net income, net of tax (60)us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesNetOfTax
/ us-gaap_IncomeStatementLocationAxis
= ibm_OtherIncomeExpenseMember		 (99)us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesNetOfTax
/ us-gaap_IncomeStatementLocationAxis
= ibm_OtherIncomeExpenseMember		 (146)us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesNetOfTax
/ us-gaap_IncomeStatementLocationAxis
= ibm_OtherIncomeExpenseMember
Interest expense      
Unrealized gains/(losses) on cash flow hedges, before tax      
Reclassification of (gains)/losses to net income, before tax 1us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_InterestExpenseMember		 0us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_InterestExpenseMember		 6us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_InterestExpenseMember
Unrealized gains/(losses) on cash flow hedges, tax      
Reclassification of (gains)/losses to net income, tax 0us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesTax
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_InterestExpenseMember		 0us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesTax
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_InterestExpenseMember		 (3)us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesTax
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_InterestExpenseMember
Unrealized gains/(losses) on cash flow hedges, net of tax      
Reclassification of (gains)/losses to net income, net of tax $ 0us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesNetOfTax
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_InterestExpenseMember		 $ 0us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesNetOfTax
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_InterestExpenseMember		 $ 3us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesNetOfTax
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_InterestExpenseMember
[1]
These AOCI components are included in the computation of net periodic pension cost. (See note S, "Retirement-Related Benefits," on pages 131 to 145 for additional information.)