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Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 2 -Article 5 false 5 Selling, general and administrative expenses (Notes 17 and 25) 1 us-gaap_SellingGeneralAndAdministrativeExpense us-gaap true debit duration No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 2680495000 2680495 false false false 2 false true false false 249286000000 249286000 false false false 3 false true false false 322677000000 322677000 false false false 4 false true false false 317474000000 317474000 false false false xbrli:monetaryItemType monetary The aggregate total costs related to selling a firm's product and services, as well as all other general and administrative expenses. Direct selling expenses (for example, credit, warranty, and advertising) are expenses that can be directly linked to the sale of specific products. Indirect selling expenses are expenses that cannot be directly linked to the sale of specific products, for example telephone expenses, Internet, and postal charges. 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Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 7 -Article 5 false 11 Interest and dividend income 1 us-gaap_InvestmentIncomeInterestAndDividend us-gaap true credit duration No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 66215000 66215 false false false 2 false true false false 6158000000 6158000 false false false 3 false true false false 8621000000 8621000 false false false 4 false true false false 10265000000 10265000 false false false xbrli:monetaryItemType monetary Income derived from investments in debt and equity securities and on cash and cash equivalents. Interest income represents earnings which reflect the time value of money or transactions in which the payments are for the use or forbearance of money. Dividend income represents a distribution of earnings to shareholders by investee companies. 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Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 34 -Paragraph 21 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher OTS -Name Federal Regulation (FR) -Number Title 12 -Chapter V -Section 563c.102 -Paragraph 9 -Subsection II Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 9 -Article 9 false 13 Other, net 1 us-gaap_OtherNonoperatingIncomeExpense us-gaap true credit duration No definition available. false false false false false false false false false false false totallabel false 1 false true false false 3097000 3097 false false false 2 false true false false 288000000 288000 false false false 3 false true false false -17211000000 -17211000 false false false 4 false true false false -4206000000 -4206000 false false false xbrli:monetaryItemType monetary The net amount of other nonoperating income and expense, which does not qualify for separate disclosure on the income statement under materiality guidelines. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 9 -Article 5 true 14 Income from continuing operations before income taxes and equity in earnings of affiliated companies 1 us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments us-gaap true credit duration No definition available. false false false false false false false false false false false totallabel false 1 false true false false 698699000 698699 false false false 2 false true false false 64979000000 64979000 false false false 3 false true false false 128782000000 128782000 false false false 4 false true false false 322210000000 322210000 false false false xbrli:monetaryItemType monetary Sum of operating profit and nonoperating income (expense) before income (loss) from equity method investments, income taxes, extraordinary items, cumulative effects of changes in accounting principles, and noncontrolling interest. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 08 -Paragraph h -Subparagraph 1(i) -Article 4 true 15 Income taxes (Notes 1 and 16) 1 us-gaap_IncomeTaxExpenseBenefitAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 false false false 4 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 16 Current 2 us-gaap_CurrentIncomeTaxExpenseBenefit us-gaap true debit duration No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 351849000 351849 false false false 2 false true false false 32722000000 32722000 false false false 3 false true false false 60511000000 60511000 false false false 4 false true false false 104142000000 104142000 false false false xbrli:monetaryItemType monetary The component of income tax expense for the period representing amounts of income taxes paid or payable (or refundable) for the period for all income tax obligations as determined by applying the provisions of relevant enacted tax laws to relevant amounts of taxable income (loss) from continuing operations. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 6 -Section I -Subsection 7 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 109 -Paragraph 289 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 08 -Paragraph h -Article 4 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 109 -Paragraph 45 -Subparagraph a false 17 Deferred 2 us-gaap_DeferredIncomeTaxExpenseBenefit us-gaap true debit duration No definition available. false false false false false false false false false false false totallabel false 1 false true false false -79118000 -79118 false false false 2 false true false false -7358000000 -7358000 false false false 3 false true false false -18218000000 -18218000 false false false 4 false true false false 11652000000 11652000 false false false xbrli:monetaryItemType monetary The component of income tax expense for the period representing the net change in the entity's deferred tax assets and liabilities pertaining to continuing operations. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 6 -Section I -Subsection 7 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 109 -Paragraph 45 -Subparagraph b Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 28 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 109 -Paragraph 289 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 08 -Paragraph h -Article 4 true 18 Total 2 us-gaap_IncomeTaxExpenseBenefit us-gaap true debit duration No definition available. false false false false false false false false false false false totallabel false 1 false true false false 272731000 272731 false false false 2 false true false false 25364000000 25364000 false false false 3 false true false false 42293000000 42293000 false false false 4 false true false false 115794000000 115794000 false false false xbrli:monetaryItemType monetary The sum of the current income tax expense (benefit) and the deferred income tax expense (benefit) pertaining to continuing operations. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 08 -Paragraph h -Article 4 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 109 -Paragraph 45 -Subparagraph a, b true 19 Income from continuing operations before equity in earnings of affiliated companies 1 kmtuf_IncomeFromContinuingOperationsBeforeMinorityInterestsAndEquityInEarningsOfAffiliatedCompanies kmtuf false credit duration Income from continuing operations before minority interests and equity in earnings of affiliated companies. false false false false false false false false false false false verboselabel false 1 false true false false 425968000 425968 false false false 2 false true false false 39615000000 39615000 false false false 3 false true false false 86489000000 86489000 false false false 4 false true false false 206416000000 206416000 false false false xbrli:monetaryItemType monetary Income from continuing operations before minority interests and equity in earnings of affiliated companies. No authoritative reference available. false 20 Equity in earnings of affiliated companies 1 us-gaap_IncomeLossFromEquityMethodInvestments us-gaap true credit duration No definition available. false false false false false false false false false false false totallabel false 1 false true false false 17075000 17075 false false false 2 false true false false 1588000000 1588000 false false false 3 false true false false 396000000 396000 false false false 4 false true false false 6845000000 6845000 false false false xbrli:monetaryItemType monetary This item represents the entity's proportionate share for the period of the net income (loss) of its investee (such as unconsolidated subsidiaries and joint ventures) to which the equity method of accounting is applied. Such amount typically reflects adjustments similar to those made in preparing consolidated statements, including adjustments to eliminate intercompany gains and losses, and to amortize, if appropriate, any difference between cost and underlying equity in net assets of the investee at the date of investment. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 18 -Paragraph 19 -Subparagraph c Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 11 -Article 7 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 28 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 9 -Article 5 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 18 -Paragraph 6 -Subparagraph b true 21 Income from continuing operations 1 us-gaap_IncomeLossFromContinuingOperations us-gaap true credit duration No definition available. false false false false false false false false false false false totallabel false 1 false true false false 443043000 443043 false false false 2 false true false false 41203000000 41203000 false false false 3 false true false false 86885000000 86885000 false false false 4 false true false false 213261000000 213261000 false false false xbrli:monetaryItemType monetary 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, but after deduction of those portions of income or loss from continuing operations that are allocable to noncontrolling interests, if any. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 29 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 28 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph b(1) true 22 Income from discontinued operations less applicable income taxes (Note 4) 1 us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity us-gaap true credit duration No definition available. false false false false false false false false false false false totallabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 false false false 4 false true false false 4967000000 4967000000 false false false xbrli:monetaryItemType monetary This element represents the overall income (loss) from a disposal group apportioned to the parent that is classified as a component of the entity, net of income tax, reported as a separate component of income before extraordinary items and the cumulative effect of accounting changes after deduction or consideration of the amount which may be allocable to noncontrolling interests, if any. Includes the following (net of tax): income (loss) from operations during the phase-out period, gain (loss) on disposal, provision (or any reversals of earlier provisions) for loss on disposal, and adjustments of a prior period gain (loss) on disposal. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 29 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 28 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph b(2) true 23 Net income 1 us-gaap_ProfitLoss us-gaap true credit duration No definition available. false false false false false false false false false false false totallabel false 1 false true false false 443043000 443043 false false false 2 false true false false 41203000000 41203000 false false false 3 false true false false 86885000000 86885000 false false false 4 false true false false 218228000000 218228000 false false false xbrli:monetaryItemType monetary The consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph A1, A4, A5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 5 -Subparagraph b Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 29 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph a Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph c(1) true 24 Less net income attributable to noncontrolling interests 1 us-gaap_NetIncomeLossAttributableToNoncontrollingInterest us-gaap true debit duration No definition available. false false false false false false false false false false true negatedtotal false 1 false true false false -82194000 -82194 false false false 2 false true false false -7644000000 -7644000 false false false 3 false true false false -8088000000 -8088000 false false false 4 false true false false -9435000000 -9435000 false false false xbrli:monetaryItemType monetary The portion of net income (loss) attributable to the noncontrolling interest (if any) deducted in order to derive the portion attributable to the parent. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph a Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph c(1) Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph A1, A4, A5 true 25 Net income attributable to Komatsu Ltd. 1 us-gaap_NetIncomeLoss us-gaap true credit duration No definition available. false false false false false false false false false false false totallabel false 1 true true false false 360849000 360849 false false false 2 true true false false 33559000000 33559000 false false false 3 true true false false 78797000000 78797000 false false false 4 true true false false 208793000000 208793000 false false false xbrli:monetaryItemType monetary The portion of consolidated profit or loss for the period, net of income taxes, which is attributable to the parent. If the entity does not present consolidated financial statements, the amount of profit or loss for the period, net of income taxes. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 19 -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph d Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph A7 -Appendix A Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph a Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 20 -Article 9 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 130 -Paragraph 10, 15 Reference 7: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Emerging Issues Task Force (EITF) -Number 87-21 Reference 8: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 28, 29, 30 true 27 Income from continuing operations attributable to Komatsu Ltd.: 2 us-gaap_IncomeLossBeforeExtraordinaryItemsAndCumulativeEffectOfChangeInAccountingPrinciplePerBasicShareAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 false false false 4 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 28 Basic 3 us-gaap_IncomeLossFromContinuingOperationsPerBasicShare us-gaap true na duration No definition available. false false false false false false false false false false false verboselabel true 1 true true false false 37.28 37.28 false false false 2 true true false false 34.67 34.67 false false false 3 true true false false 79.95 79.95 false false false 4 true true false false 204.88 204.88 false false false us-types:perShareItemType decimal The amount of income (loss) from continuing operations per each share of common stock outstanding during the reporting period. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 21 -Article 9 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 128 -Paragraph 36, 37, 38 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 20 -Article 5 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 18 -Article 7 false 29 Diluted 3 us-gaap_IncomeLossFromContinuingOperationsPerDilutedShare us-gaap true na duration No definition available. false false false false false false false false false false false verboselabel true 1 true true false false 37.26 37.26 false false false 2 true true false false 34.65 34.65 false false false 3 true true false false 79.89 79.89 false false false 4 true true false false 204.61 204.61 false false false us-types:perShareItemType decimal The amount of income (loss) from continuing operations 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. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 21 -Article 9 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 128 -Paragraph 11, 12, 36, 37, 38 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 128 -Paragraph 40 -Subparagraph a Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 20 -Article 5 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 18 -Article 7 false 30 Income from discontinued operations attributable to Komatsu Ltd.: 2 us-gaap_IncomeLossBeforeExtraordinaryItemsAndCumulativeEffectOfChangeInAccountingPrinciplePerDilutedShareAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 false false false 4 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 31 Basic 3 us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare us-gaap true na duration No definition available. false false false false false false false false false false false verboselabel true 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 false false false 4 true true false false 4.99 4.99 false false false us-types:perShareItemType decimal The amount of income (loss) from disposition of discontinued operations, net of related tax effect, per each share of common stock outstanding during the reporting period. 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Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 5 -Section E -Paragraph Question 3 false 33 Net income attributable to Komatsu Ltd.: 2 kmtuf_NetIncomeAbstract kmtuf false na duration Net income. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 false false false 4 false false false false 0 0 false false false xbrli:stringItemType string Net income. false 34 Basic 3 us-gaap_EarningsPerShareBasic us-gaap true na duration No definition available. false false false false false false false false false false false verboselabel true 1 true true false false 37.28 37.28 false false false 2 true true false false 34.67 34.67 false false false 3 true true false false 79.95 79.95 false false false 4 true true false false 209.87 209.87 false false false us-types:perShareItemType decimal The amount of net income or loss for the period per each share of common stock outstanding during the reporting period. 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