Fair Value of Financial Instruments and Concentration of Credit Risk (Details) (JPY ¥) In Millions	12 Months Ended
Mar. 31, 2011	Mar. 31, 2010
Fair Value of Financial Instruments and Concentration of Credit Risk
Finance receivables-net, Carrying Value	¥ 193,382	¥ 211,363
Long-term trade accounts receivable, Carrying Value	50,971	47,610
Finance receivables-net, Fair Value	193,749	212,021
Long-term trade accounts receivable, Fair Value	53,725	50,409
Long-term debt, Carrying Value	(274,198)	(308,779)
Long-term debt, Fair Value	¥ (274,507)	¥ (309,258)

The aggregate of amounts due from customers or clients for goods or services that have been delivered or sold in the normal course of business (both current and non-current) as well as the amounts for the current portion of long-term trade accounts receivables.

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents finance receivable both current and non-current as well as current portion of long-term trade accounts receivable.

+ Details

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Namespace Prefix:	kub
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Fair Value Disclosures [Abstract]

+ Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The aggregate of amounts due from customers or clients with the original contractual terms of more than one year, for goods or services that have been delivered or sold in the normal course of business, less allowance for doubtful accounts.

+ Details

Name:	kub_LongTermAccountsReceivableNet
Namespace Prefix:	kub
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

+ Details

Name:	kub_LongTermDebtFairValue
Namespace Prefix:	kub
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. Amounts due from customers or clients for goods or services (including trade receivables) that have been delivered or sold in the normal course of business, as well as any other amounts due from others, including related parties, which may be included in accounts receivable as categorized on the statement of financial position.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 03
-Paragraph 3
-Subparagraph a, b
-Article 5

+ Details

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Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Including current and noncurrent portions, aggregate carrying amount of long-term borrowings as of the balance sheet date before deducting unamortized discount or premiums (if any). May include notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt, which had initial maturities beyond one year or beyond the normal operating cycle, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name FASB Staff Position (FSP)
-Number APB14-1
-Paragraph 31
-Subparagraph b

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 20
-Article 5

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 22
-Article 5

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 03
-Paragraph 16
-Article 9

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant