Note 6 - Investments in Affordable Housing and Alternative Energy Partnerships - Usage of Affordable Housing and Other Tax Credits Including Energy Tax Credit (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Affordable housing and other tax credits recognized	$ 32,395	$ 29,524	$ 26,459
Alternative energy tax credits recognized	$ 41,320	$ 4,707	$ 6,337

The amount of affordable housing and other tax credits recognized during the period.

No definition available.

Name:	caty_AffordableHousingAndOtherTaxCreditsRecognized
Namespace Prefix:	caty_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration