The percentage of approved forbearance to total residential mortgages for financing receivable.

No definition available.

Name:	caty_FinancingReceivableApprovedForbearancePercentageOfTotalResidentialMortgageLoans
Namespace Prefix:	caty_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The number of financing receivables contracts.

+ References

No definition available.

+ Details

Name:	caty_FinancingReceivableNumberOfContracts
Namespace Prefix:	caty_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

The number of financing receivable contracts with approved forbearance requests.

+ References

No definition available.

+ Details

Name:	caty_FinancingReceivableNumberOfContractsWithApprovedForbearanceRequests
Namespace Prefix:	caty_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

The number of financing receivables contracts with modifications.

+ References

No definition available.

+ Details

Name:	caty_FinancingReceivableNumberOfContractsWithModifications
Namespace Prefix:	caty_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage of total modified commercial loans.

+ References

No definition available.

+ Details

Name:	caty_FinancingReceivablePercentageOfTotalModifiedCommercialLoans
Namespace Prefix:	caty_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The percentage of financing receivable with modifications to total commercial real estate loans.

+ References

No definition available.

+ Details

Name:	caty_FinancingReceivableWithModificationsPercentageOfTotalCommercialRealEstateLoans
Namespace Prefix:	caty_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount before allowance of loans and leases held in portfolio with approved forbearance requests, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

+ References

No definition available.

+ Details

Name:	caty_LoansAndLeasesReceivableWithApprovedForbearanceRequestsGross
Namespace Prefix:	caty_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount before allowance of loans and leases held in portfolio with modifications, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

+ References

No definition available.

+ Details

Name:	caty_LoansAndLeasesReceivableWithModificationsGross
Namespace Prefix:	caty_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=121593590&loc=d3e4428-111522

+ Details

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

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ResidentialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Data Type:	na
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- Details

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Namespace Prefix:
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Note 21 - Subsequent Events (Details Textual) $ in Thousands	May 01, 2020 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Loans and Leases Receivable, Gross, Total		$ 15,534,212	$ 15,075,481
Commercial Real Estate Portfolio Segment [Member]
Loans and Leases Receivable, Gross, Total		7,422,585	7,275,262
Commercial Portfolio Segment [Member]
Loans and Leases Receivable, Gross, Total		2,973,078	2,778,744
Residential Portfolio Segment [Member]
Loans and Leases Receivable, Gross, Total		$ 4,173,876	$ 4,088,586
Subsequent Event [Member] \| Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Number of Contracts with Modifications	504
Loans and Leases Receivable with Modifications, Gross	$ 978,000
Financing Receivable, Percentage of Total Commercial Real Estate Loans	13.40%
Subsequent Event [Member] \| Commercial Portfolio Segment [Member]
Financing Receivable, Number of Contracts with Modifications	46
Loans and Leases Receivable with Modifications, Gross	$ 123,200
Financing Receivable, Percentage of Total Commercial Loans	4.10%
Subsequent Event [Member] \| Residential Portfolio Segment [Member]
Financing Receivable, Number of Contracts with Approved Forbearance Requests	1,094
Loans and Leases Receivable with Approved Forbearance Requests, Gross	$ 477,700
Financing Receivable, Percentage of Total Residential Mortgage Loans	11.50%
Subsequent Event [Member] \| SBA's Paycheck Protection Program [Member]
Financing Receivable, Number of Contracts	964
Loans and Leases Receivable, Gross, Total	$ 242,700