Note 5 - Loans (Details) - Non-Accrual Loans (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Note 5 - Loans (Details) - Non-Accrual Loans [Line Items]
Non-accrual portfolio loans	$ 83,183	$ 103,902	$ 201,197
Non-accrual loans held-for-sale			760
Total non-accrual loans	83,183	103,902	201,957
Contractual interest due	5,599	9,305	5,330
Nonaccrual Loans [Member]
Note 5 - Loans (Details) - Non-Accrual Loans [Line Items]
Contractual interest due	5,851	6,621	13,049
Interest recognized	22	1,006	71
Net interest foregone	$ 5,829	$ 5,615	$ 12,978

Non accrual loans.

No definition available.

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Period Type:	instant

- Definition

Non accrual loans held for sale.

+ References

No definition available.

+ Details

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

- Definition

Non accrual portfolio loans.

+ References

No definition available.

+ Details

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

- Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of interest income recognized that the financing receivables (with related allowance for credit losses and without a related allowance for credit losses) were impaired.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 15

-Subparagraph (c)(2)

-URI http://asc.fasb.org/extlink&oid=28368275&loc=d3e5212-111524

+ Details

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

- Definition

Amount of interest income recognized on a cash-basis method of accounting that the financing receivables (with related allowance for credit losses and without a related allowance for credit losses) were impaired.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 15

-Subparagraph (c)(3)

-URI http://asc.fasb.org/extlink&oid=28368275&loc=d3e5212-111524

+ Details

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Data Type:	xbrli:monetaryItemType
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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

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 40

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=25495931&loc=d3e18794-111554

+ Details

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