Name:	caty_FederalHomeLoanBankStockShares
Namespace Prefix:	caty_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

Commercial loans as a percentage of gross loans.

No definition available.

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

Commercial mortgage loans as a percentage of gross loans.

No definition available.

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

Maximum loan size portfolio stratification, homogenous portfolio.

No definition available.

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

Represents the minimum stock requirement on outstanding federal home loan bank borrowings, in shares.

No definition available.

Name:	caty_MinimumStockRequirementOnOutstandingFederalHomeLoanBankBorrowingsShares
Namespace Prefix:	caty_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

Number of limited Partnerships in housing investments.

No definition available.

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

Percentage of subsidiaries common securities owned by parent company.

No definition available.

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

Residential mortgages properties percentage.

No definition available.

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

Federal Home Loan Bank (FHLB) stock represents an equity interest in a FHLB. It does not have a readily determinable fair value because its ownership is restricted and it lacks a market (liquidity).

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 325
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=75031641&loc=d3e63345-112809

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

Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13854-109267

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13777-109266

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

Name:	us-gaap_GoodwillImpairmentLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 9
-Subparagraph (a),(b)
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32639-109319

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(h))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Name:	us-gaap_IncomeTaxExpenseBenefit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

No definition available.

Name:	us-gaap_NumberOfOperatingSegments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

No definition available.