Note 2 - Cash and Cash Equivalents (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2013	Dec. 31, 2012
Cash and Cash Equivalents [Abstract]
Average Reserve Balances Required To Be Maintained With Federal Bank	$ 6.5	$ 12.9

Average reserve balances required to be maintained with the federal bank.

No definition available.

Name:	caty_AverageReserveBalancesRequiredToBeMaintainedWithFederalBank
Namespace Prefix:	caty_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration