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It also includes other kinds of accounts that have the general characteristics of demand deposits in that the Entity may deposit additional funds at any time and also effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months. 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No authoritative reference available. false 7 Trade notes and accounts receivable, less allowance for doubtful receivables of 14,941 million ($160,656 thousand) in 2010 and 15,330 million in 2009 (Notes 1, 5 and 26) 3 us-gaap_AccountsNotesAndLoansReceivableNetCurrent us-gaap true debit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 4813903000 4813903 false false false 2 false true false false 373901000000 373901000 false false false 3 false true false false 447693000000 447693000 false false false xbrli:monetaryItemType monetary The aggregate of amounts due from customers or clients, within one year of the balance sheet date (or one operating cycle, if longer), for goods or services that have been delivered or sold in the normal course of business and an amount representing an agreement for an unconditional promise by the maker to pay the entity (holder) a definite sum of money at a future date within one year of the balance sheet, reduced to their estimated net realizable fair value by an allowance established by the entity of the amount it deems uncertain of collection and net of any write-downs taken for collection uncertainty on the part of the holder, respectively. 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Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 12 -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 1 -Subparagraph f -Article 7 true 16 Total investments 3 us-gaap_LongTermInvestments us-gaap true debit instant No definition available. false false false false false false false false false false false totallabel false 1 false true false false 934064000 934064 false false false 2 false true false false 85120000000 85120000 false false false 3 false true false false 86868000000 86868000 false false false xbrli:monetaryItemType monetary The total amount of investments that are intended to be held for an extended period of time (longer than one operating cycle). No authoritative reference available. true 17 Property, plant and equipment-less accumulated depreciation (Notes 1, 9, 10 and 17) 2 us-gaap_PropertyPlantAndEquipmentNet us-gaap true debit instant No definition available. false false false false false false false false false false false totallabel false 1 false true false false 5646237000 5646237 false false false 2 false true false false 525462000000 525462000 false false false 3 false true false false 525100000000 525100000 false false false xbrli:monetaryItemType monetary Tangible assets that are held by an entity for use in the production or supply of goods and services, for rental to others, or for administrative purposes and that are expected to provide economic benefit for more than one year; net of accumulated depreciation. Examples include land, buildings, and production equipment. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 13 -Subparagraph a -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 12 -Paragraph 5 -Subparagraph b, c Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 8 -Article 7 true 18 Goodwill (Notes 1 and 11) 2 us-gaap_Goodwill us-gaap true debit instant No definition available. false false false false false false false false false false false totallabel false 1 false true false false 317957000 317957 false false false 2 false true false false 28661000000 28661000 false false false 3 false true false false 29570000000 29570000 false false false xbrli:monetaryItemType monetary Carrying amount as of the balance sheet date, which is the cumulative amount paid, adjusted for any amortization recognized prior to adoption of FAS 142 and for any impairment charges, in excess of the fair value of net assets acquired in one or more business combination transactions. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 142 -Paragraph 43 true 19 Other intangible assets (Notes 1 and 11) 2 us-gaap_IntangibleAssetsNetExcludingGoodwill us-gaap true debit instant No definition available. false false false false false false false false false false false totallabel false 1 false true false false 663753000 663753 false false false 2 false true false false 60346000000 60346000 false false false 3 false true false false 61729000000 61729000 false false false xbrli:monetaryItemType monetary Sum of the carrying amounts of all intangible assets, excluding goodwill, as of the balance sheet date, net of accumulated amortization and impairment charges. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 142 -Paragraph 42, 45 true 20 Deferred income taxes and other assets (Notes 1, 16, 20, 21, 22 and 26) 2 kmtuf_DeferredIncomeTaxesAndOtherAssets kmtuf false debit instant Deferred income taxes and other assets. false false false false false false false false false false false totallabel false 1 false true false false 695645000 695645 false false false 2 false true false false 63262000000 63262000 false false false 3 false true false false 64695000000 64695000 false false false xbrli:monetaryItemType monetary Deferred income taxes and other assets. 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No authoritative reference available. false 26 Trade notes, bills and accounts payable 3 us-gaap_AccountsPayableCurrent us-gaap true credit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 2226065000 2226065 false false false 2 false true false false 214375000000 214375000 false false false 3 false true false false 207024000000 207024000 false false false xbrli:monetaryItemType monetary Carrying value as of the balance sheet date of liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received that are used in an entity's business. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer). Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 19 -Subparagraph a -Article 5 false 27 Income taxes payable (Note 16) 3 us-gaap_AccruedIncomeTaxesCurrent us-gaap true credit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 236602000 236602 false false false 2 false true false false 10818000000 10818000 false false false 3 false true false false 22004000000 22004000 false false false xbrli:monetaryItemType monetary Carrying amount as of the balance sheet date of the unpaid sum of the known and estimated amounts payable to satisfy all currently due domestic and foreign income tax obligations. 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No authoritative reference available. true 29 Total current liabilities 3 us-gaap_LiabilitiesCurrent us-gaap true credit instant No definition available. false false false false false false false false false false false totallabel false 1 false true false false 6900495000 6900495 false false false 2 false true false false 732287000000 732287000 false false false 3 false true false false 641746000000 641746000 false false false xbrli:monetaryItemType monetary Total obligations incurred as part of normal operations that are expected to be paid during the following twelve months or within one business cycle, if longer. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 21 -Article 5 true 30 Long-term liabilities 2 us-gaap_LiabilitiesNoncurrentAbstract 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 xbrli:stringItemType string No definition available. false 31 Long-term debt (Notes 10, 12, 17 and 21) 3 us-gaap_LongTermDebtAndCapitalLeaseObligations us-gaap true credit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 3838548000 3838548 false false false 2 false true false false 292106000000 292106000 false false false 3 false true false false 356985000000 356985000 false false false xbrli:monetaryItemType monetary Sum of the carrying values as of the balance sheet date of all long-term debt, which is debt initially having maturities due after one year from the balance sheet date or beyond the operating cycle, if longer, but excluding the portions thereof scheduled to be repaid within one year or the normal operating cycle, if longer plus capital lease obligations due to be paid more than one year after the balance sheet date. 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This caption alerts the reader that one or more notes to the financial statements disclose pertinent information about the entity's commitments and contingencies. 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This item includes treasury stock repurchased by the entity. Note: elements for number of common shares, par value and other disclosure concepts are in another section within stockholders' equity. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 30 -Article 5 false 41 Capital surplus 4 us-gaap_AdditionalPaidInCapitalCommonStock us-gaap true credit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 1509903000 1509903 false false false 2 false true false false 140092000000 140092000 false false false 3 false true false false 140421000000 140421000 false false false xbrli:monetaryItemType monetary Value received from shareholders in common stock-related transactions that are in excess of par value or stated value and amounts received from other stock-related transactions. 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Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 31 -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 5 -Paragraph 15 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 24 -Subparagraph a(4) -Article 7 false 44 Unappropriated 5 us-gaap_RetainedEarningsUnappropriated us-gaap true credit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 7785914000 7785914 false false false 2 false true false false 719222000000 719222000 false false false 3 false true false false 724090000000 724090000 false false false xbrli:monetaryItemType monetary A segregation of retained earnings which is available for dividend distribution. Earnings not paid out as dividends but instead reinvested in the core business or used to pay off debt. Unappropriated profit is part of shareholder equity. Also called Cumulative distributions or earned surplus or accumulated earnings or unappropriated profit. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 31 -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 24 -Subparagraph a(4) -Article 7 false 45 Accumulated other comprehensive income (loss) (Notes 1, 7, 13 and 15) 4 us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax us-gaap true credit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false -1028323000 -1028323 false false false 2 false true false false -105744000000 -105744000 false false false 3 false true false false -95634000000 -95634000 false false false xbrli:monetaryItemType monetary Accumulated change in equity from transactions and other events and circumstances from non-owner sources, net of tax effect, at fiscal year-end. Excludes Net Income (Loss), and accumulated changes in equity from transactions resulting from investments by owners and distributions to owners. Includes foreign currency translation items, certain pension adjustments, and unrealized gains and losses on certain investments in debt and equity securities as well as changes in the fair value of derivatives related to the effective portion of a designated cash flow hedge. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Article 3 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 12 -Paragraph 10 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 130 -Paragraph 14, 17, 26 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 31 -Article 5 false 46 Treasury stock at cost, 30,704,084 shares in 2010 and 30,921,768 shares in 2009 (Notes 14) 4 us-gaap_TreasuryStockValue us-gaap true debit instant No definition available. false false false false false false false false false false true negatedtotal false 1 false true false false -373709000 -373709 false false false 2 false true false false -34971000000 -34971000 false false false 3 false true false false -34755000000 -34755000 false false false xbrli:monetaryItemType monetary Value of common and preferred shares of an entity that were issued, repurchased by the entity, and are held in its treasury. Treasury stock is issued but is not outstanding. This stock has no voting rights and receives no dividends. Note that treasury stock may be recorded at its total cost or separately as par (or stated) value and additional paid in capital. Note: number of treasury shares concept is in another section within stockholders' equity. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name FASB Technical Bulletin (FTB) -Number 85-6 -Paragraph 3 true 47 Total Komatsu Ltd. shareholders' equity 3 us-gaap_StockholdersEquity us-gaap true credit instant No definition available. false false false false false false false false false false false totallabel false 1 false true false false 8967473000 8967473 false false false 2 false true false false 814941000000 814941000 false false false 3 false true false false 833975000000 833975000 false false false xbrli:monetaryItemType monetary Total of all Stockholders' Equity (deficit) items, net of receivables from officers, directors owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph A3 -Appendix A Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 4 -Section E Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 29, 30, 31 -Article 5 true 48 Noncontrolling interests 3 us-gaap_MinorityInterest us-gaap true credit instant No definition available. false false false false false false false false false false false totallabel false 1 false true false false 460473000 460473 false false false 2 false true false false 33393000000 33393000 false false false 3 false true false false 42824000000 42824000 false false false xbrli:monetaryItemType monetary Total of all Stockholders' Equity (deficit) items, net of receivables from officers, directors owners, and affiliates of the entity which is directly or indirectly attributable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). 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The entity including portions attributable to the parent and noncontrolling interests is sometimes referred to as the economic entity. This excludes temporary equity and is sometimes called permanent equity. 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