Note 5 - Loans - Average Balance and Interest Income Recognized Related to Non-accrual Loans (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Average Recorded Investment	$ 71,830	$ 71,371
Interest Income Recognized	321	435	$ 1,074
Non-accrual portfolio loans	66,681	68,854	65,846
Contractual interest due	6,270	4,620	4,032
Net interest foregone	5,949	4,185	$ 2,958
Commercial Portfolio Segment [Member]
Average Recorded Investment	18,008	28,109
Interest Income Recognized	3	4
Real Estate Construction Portfolio Segment [Member]
Average Recorded Investment	6,336	28,983
Interest Income Recognized	0	0
Commercial Real Estate Portfolio Segment [Member]
Average Recorded Investment	35,742	14,251
Interest Income Recognized	318	405
Residential Mortgage and Equity Lines Portfolio Segment [Member]
Average Recorded Investment	11,743	28
Interest Income Recognized	0	$ 26
Installment and Other Loans [Member ]
Average Recorded Investment	1
Interest Income Recognized	$ 0

Amount of average recorded investments of financing receivable on nonaccrual status. Excludes net investment in lease.

No definition available.

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of contractual interest due on financing receivable on nonaccrual status.

+ References

No definition available.

+ Details

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

- Definition

Reflects the amount of additional interest income that would have been recorded if impaired or nonperforming loans were instead current, in compliance with their original terms, and outstanding throughout the reporting period or since origination (if held for part of the period).

+ References

No definition available.

+ Details

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

- Definition

Loans in non-accrual status classified as portfolio loans.

+ References

No definition available.

+ Details

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Namespace Prefix:	caty_
Data Type:	xbrli:monetaryItemType
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- Definition

Amount of interest income on financing receivable on nonaccrual status.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 16
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479319/326-20-50-16

+ Details

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- Details

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- Details

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- Details

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- Details

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- Details

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