Allowance For Doubtful Accounts And Credit Losses (Schedule Of Allowance For Credit Losses On Finance Receivables) (Detail) (JPY ¥) In Millions, unless otherwise specified	12 Months Ended
Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2010
Allowance for credit losses on finance receivables:
Balance at beginning of year	¥ 3,101	¥ 1,706	¥ 1,586
Provision	2,268	2,304	855
Charge-offs	(945)	(780)	(327)
Other	(327)	(129)	(408)
Balance at end of year	¥ 4,097	¥ 3,101	¥ 1,706

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).

No definition available.

Name:	kub_ProvisionForDoubtfulFinanceReceivables
Namespace Prefix:	kub_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration