The amount of deferred gain on early termination of derivative recognized.

No definition available.

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

- Definition

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

+ References

No definition available.

+ Details

Name:	caty_DerivativeOriginalMaturity
Namespace Prefix:	caty_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Outstanding notional amount specified by the derivative(s). Expressed as an absolute value.

+ References

No definition available.

+ Details

Name:	caty_DerivativeOutstandingNotionalAmount
Namespace Prefix:	caty_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Definition

The notational amount of a loan.

+ References

No definition available.

+ Details

Name:	caty_LoanNotationalAmount
Namespace Prefix:	caty_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Definition

Indicates line item in statement of financial position that includes derivative asset.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4A
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-4A

+ Details

Name:	us-gaap_DerivativeAssetStatementOfFinancialPositionExtensibleEnumeration
Namespace Prefix:	us-gaap_
Data Type:	enum2:enumerationSetItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of increase in the fair value of derivatives recognized in the income statement.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4A
-Subparagraph (b)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-4A

+ Details

Name:	us-gaap_DerivativeGainOnDerivative
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Indicates line item in statement of financial position that includes derivative liability.

+ References

+ Details

Name:	us-gaap_DerivativeLiabilityStatementOfFinancialPositionExtensibleEnumeration
Namespace Prefix:	us-gaap_
Data Type:	enum2:enumerationSetItemType
Balance Type:	na
Period Type:	instant

- Definition

Nominal or face amount used to calculate payment on derivative.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-1B

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1A
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-1A

+ Details

Name:	us-gaap_DerivativeNotionalAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Definition

Period the derivative contract is outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_DerivativeTermOfContract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of asset hedged in fair value hedging relationship.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 181
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480401/815-10-55-181

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4EE
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-4EE

+ Details

Name:	us-gaap_HedgedAssetFairValueHedge
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of cumulative increase (decrease) in fair value of hedged asset in fair value hedge, attributable to hedged risk, in portfolio layer hedging relationship.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 181
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480401/815-10-55-181

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4EEE
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-4EEE

+ Details

Name:	us-gaap_HedgedAssetFairValueHedgeLastOfLayerCumulativeIncreaseDecrease
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Including the current and noncurrent portions, carrying value as of the balance sheet date of long-term debt (with maturities initially due after one year or beyond the operating cycle if longer) identified as Junior Subordinated Notes, which have a lower priority than senior instruments.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-SubTopic 10
-Topic 210
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478546/942-210-S99-1

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 944
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16)(a)(2))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478777/944-210-S99-1

+ Details

Name:	us-gaap_JuniorSubordinatedNotes
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_InterestRateSwapMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis=us-gaap_CashFlowHedgingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_HedgingDesignationAxis=us-gaap_DesignatedAsHedgingInstrumentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_CounterpartyNameAxis=caty_CentralCounterpartiesCcpMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis=us-gaap_FairValueHedgingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_InterestRateContractMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=caty_LoansReceivableWithPartialTermHedgingDesignationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Note 15 - Financial Derivatives (Details Textual) - USD ($)		12 Months Ended
	May 31, 2014	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Junior Subordinated Notes, Total	$ 119,100,000	$ 119,136	$ 119,136
Derivative Asset, Statement of Financial Position [Extensible Enumeration]		Other Assets
Derivative Liability, Statement of Financial Position [Extensible Enumeration]		Other Liabilities
Interest Rate Swap [Member] \| Cash Flow Hedging [Member] \| Designated as Hedging Instrument [Member]
Derivative Outstanding, Notional Amount	$ 119,100,000	$ 680,500,000	650,900,000
Derivative, Notional Amount		32,700,000	38,600,000
Derivative Original Maturity (Year)	10 years
Deferred Gain on Early Termination of Derivative				$ 4,000,000
Interest Rate Swap [Member] \| Cash Flow Hedging [Member] \| Designated as Hedging Instrument [Member] \| Central Counterparties (CCP) [Member]
Derivative, Notional Amount		0	0
Interest Rate Swap [Member] \| Fair Value Hedging [Member] \| Designated as Hedging Instrument [Member]
Derivative, Notional Amount		875,117,000	1,156,007,000
Interest Rate Swap [Member] \| Fair Value Hedging [Member] \| Designated as Hedging Instrument [Member] \| Central Counterparties (CCP) [Member]
Derivative, Notional Amount		572,800,000	846,900,000
Derivative, Gain on Derivative		158,000	257,000
Interest Rate Contract [Member] \| Fair Value Hedging [Member] \| Designated as Hedging Instrument [Member]
Derivative Outstanding, Notional Amount		81,300,000	88,500,000
Derivative, Notional Amount		$ 3,300,000	4,200,000
Interest Rate Contract [Member] \| Fair Value Hedging [Member] \| Designated as Hedging Instrument [Member] \| Minimum [Member]
Derivative, Term of Contract (Year)		3 years
Interest Rate Contract [Member] \| Fair Value Hedging [Member] \| Designated as Hedging Instrument [Member] \| Maximum [Member]
Derivative, Term of Contract (Year)		10 years
Loans Receivable with Partial-term Hedging Designation [Member]
Derivative, Notional Amount		$ 321,000,000	3,800,000
Hedged Asset, Fair Value Hedge		793,800,000	1,070,000,000.00
Loan, Notational Amount		1,320,000,000	1,780,000,000
Hedged Asset, Fair Value Hedge, Portfolio Layer Method, Hedged Layer, Fair Value, Cumulative Increase (Decrease)		$ 1,200,000	$ 2,000,000