Reflects the amount of the specific reserve related to a troubled debt restructuring.

No definition available.

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

- Definition

Percentage of charge-off to contractual balances for impaired loans.

+ References

No definition available.

+ Details

Name:	caty_PercentageOfChargeOffToContractualBalancesForImpairedLoans
Namespace Prefix:	caty_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Period Loan Is In Payment Default

+ References

No definition available.

+ Details

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

- Definition

Amount of financing receivable modified as troubled debt restructuring.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI https://asc.fasb.org/extlink&oid=123577603&loc=SL6953676-111524

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 40
-Section 50
-Paragraph 4
-URI https://asc.fasb.org/extlink&oid=121585226&loc=d3e18845-111554

+ Details

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

- Definition

Amount of financing receivable modified as troubled debt restructuring within previous 12 months, with subsequent payment default.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 34
-Subparagraph (a)(2)
-URI https://asc.fasb.org/extlink&oid=123577603&loc=SL6953682-111524

+ Details

Name:	us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 14A
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=123577603&loc=SL6953550-111524

+ Details

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

- Definition

Amount of unfunded portion of contractual agreement to lend funds to borrower for financing receivable modified as troubled debt restructuring.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 40
-Section 50
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=121585226&loc=d3e18794-111554

+ Details

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

- 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_ClassOfFinancingReceivableTypeOfBorrowerAxis=caty_NonaccrualLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ClassOfFinancingReceivableTypeOfBorrowerAxis=caty_AccruingTroubledDebtRestructuringMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ClassOfFinancingReceivableTypeOfBorrowerAxis=caty_NonaccruingTroubledDebtRestructuringMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Note 9 - Loans (Details Textual) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
Note 9 - Loans (Details Textual) - USD ($)	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Impaired Financing Receivable, Recorded Investment	$ 68,125,000		$ 68,125,000		$ 65,846,000
Percentage Of Charge Off To Contractual Balances For Impaired Loans	12.20%		12.20%		10.70%
Financing Receivables, Impaired, Troubled Debt Restructuring, Specific Reserve	$ 0	$ 0	$ 0	$ 0
Financing Receivable, Troubled Debt Restructuring, Subsequent Default			0
Financing Receivable, Troubled Debt Restructuring, Commitment to Lend	0		$ 0
Minimum [Member]
Period Loan Is In Payment Default (Day)			60 days
Maximum [Member]
Period Loan Is In Payment Default (Day)			90 days
Nonaccrual Loans [Member]
Impaired Financing Receivable, Recorded Investment	68,100,000		$ 68,100,000		$ 65,800,000
Accruing Troubled Debt Restructuring [Member]
Financing Receivable, Troubled Debt Restructuring	15,200,000		15,200,000		12,800,000
Financing Receivables, Impaired, Troubled Debt Restructuring, Specific Reserve			10,000		7,000
Non-accruing Troubled Debt Restructuring [Member]
Financing Receivable, Troubled Debt Restructuring	$ 6,400,000		6,400,000		8,200,000
Financing Receivables, Impaired, Troubled Debt Restructuring, Specific Reserve			$ 499,000		$ 3,000