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, 2013	Mar. 31, 2012	Mar. 31, 2011
Allowance for credit losses on finance receivables:
Balance at beginning of year	¥ 4,097	¥ 3,101	¥ 1,706
Provision	2,531	2,268	2,304
Charge-offs	(628)	(945)	(780)
Other	795	(327)	(129)
Balance at end of year	¥ 6,795	¥ 4,097	¥ 3,101

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