Allowance for Doubtful Accounts and Credit Losses (Schedule of Allowance for Credit Losses on Finance Receivables) (Details) (JPY ¥) In Millions	12 Months Ended
Mar. 31, 2011	Mar. 31, 2010	Mar. 31, 2009
Allowance for Doubtful Accounts and Credit Losses
Balance at beginning of year	¥ 1,706	¥ 1,586	¥ 1,380
Provision	2,304	855	914
Charge-offs	(780)	(327)	(308)
Other	(129)	(408)	(400)
Balance at end of year	¥ 3,101	¥ 1,706	¥ 1,586

Allowance For Doubtful Accounts And Credit Losses [Abstract]

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- Definition

Reflects the net amount of other additions and reductions in the allowance for doubtful finance receivables.

+ Details

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- Definition

Reduction to the allowance for doubtful finance receivables deemed uncollectible.

+ Details

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- Definition

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

+ Details

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- Definition

Amount of the current period expense charged against operations, the offset which is generally to the allowance for doubtful finance receivables for the purpose of reducing receivables to an amount that approximates their net realizable value (the amount expected to be collected).

+ Details

Name:	kub_ProvisionForDoubtfulFinanceReceivables
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Balance Type:	credit
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