Note 2 - Business Combinations (Details Textual) $ in Thousands	Feb. 07, 2022 USD ($)
HSBC Bank USA [Member]
Number Of Branch Locations	10
HSBC Bank USA West Coast Mass Market Consumer and Retail Banking Business [Member]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Financing Receivable	$ 646,100
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deposit Liabilities	$ 575,163

The amount of deposit liabilities assumed which have been recognized as of the acquisition date.

No definition available.

Name:	caty_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDepositLiabilities
Namespace Prefix:	caty_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant