Note 5 - Loans (Details) - Non-Accrual Loans - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Note 5 - Loans (Details) - Non-Accrual Loans [Line Items]
Non-accrual portfolio loans	$ 52,130	$ 70,163	$ 83,183
Non-accrual loans held-for-sale	5,944	973
Total non-accrual loans	58,074	71,136	83,183
Contractual interest due	3,997	5,339	5,599
Nonaccrual Loans [Member]
Note 5 - Loans (Details) - Non-Accrual Loans [Line Items]
Contractual interest due	5,732	6,663	5,851
Interest recognized	119	217	22
Net interest foregone	$ 5,613	$ 6,446	$ 5,829

Loans in non-accrual status.

No definition available.

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- Definition

Loans in non-accrual status classified as held-for-sale loans.

+ References

No definition available.

+ Details

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- Definition

Loans in non-accrual status classified as portfolio loans.

+ References

No definition available.

+ Details

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Namespace Prefix:	caty_
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- References

No definition available.

+ Details

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- 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=49124121&loc=d3e5212-111524

+ Details

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- 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=49124121&loc=d3e5212-111524

+ Details

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- 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

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