Sales Financing Receivables and Other Loan Receivables (Schedule of Financing Receivables - Net) (Details) (JPY ¥) In Millions	Mar. 31, 2011	Mar. 31, 2010
Unguaranteed residual values related to finance leases	¥ 0
Less: current portion	(100,437)	(104,840)
Total finance receivables-net	300,266	301,313
Long-term finance receivables-net	199,829	196,473
Retail Finance Receivable [Member]
Retail finance receivable	193,985	211,875
Less: Allowance for credit losses	(603)	(512)
Retail-net	193,382	211,363
Finance Lease Receivable [Member]
Less: Allowance for credit losses	(2,498)	(1,194)
Finance lease receivable	127,056	106,774
Less: Unearned income	(17,674)	(15,630)
Finance leases-net	¥ 106,884	¥ 89,950

The remaining (unamortized) difference between the gross investment in a lease and the cost or carrying amount, if different, of the leased property as of the balance sheet date.

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- Definition

The estimate of the lease property's economic value at the end of the lease term excluding any amounts guaranteed by either the lessee or a third-party.

+ Details

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Data Type:	xbrli:monetaryItemType
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Period Type:	instant

- Definition

Reflects the aggregate carrying amount of current and non-current finance lease receivables.

+ Details

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Balance Type:	debit
Period Type:	instant

- Definition

Reflects the aggregate carrying amount of current and non-current finance lease receivables, net of unearned income and the allowance for credit losses.

+ Details

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

- Definition

A valuation allowance for finance receivables that are expected to be uncollectible.

+ Details

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

- Definition

Reflects the aggregate carrying amount of retail loan and finance lease receivables, net of unearned income and the allowance for losses. These are collected within one year of the balance sheet date.

+ Details

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Balance Type:	debit
Period Type:	instant

- Definition

Reflects the aggregate carrying amount of current and non-current retail loan and finance lease receivables, net of unearned income and the allowance for losses.

+ Details

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

- Definition

Reflects the aggregate carrying amount of retail loan and finance lease receivables, net of unearned income and the allowance for losses. These are collected after one year of the balance sheet date.

+ Details

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- Definition

Reflects the aggregate carrying amount of current and non-current retail loan receivables.

+ Details

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

- Definition

Reflects the aggregate carrying amount of current and non-current retail loan receivables, net of the allowance for credit losses.

+ Details

Name:	kub_RetailFinanceReceivableNet
Namespace Prefix:	kub
Data Type:	xbrli:monetaryItemType
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Period Type:	instant