Name:	caty_Note11CapitalResourcesDetailsLineItems
Namespace Prefix:	caty_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Percent of senior preferred stock invested.

+ References

No definition available.

+ Details

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

- Definition

Cash received on warrant transaction.

+ References

No definition available.

+ Details

Name:	caty_SaleOfWarrantConsiderationReceivedOnTransaction
Namespace Prefix:	caty_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Per share amount received for each warrant sold in the transaction.

+ References

No definition available.

+ Details

Name:	caty_SaleOfWarrantsPricePerShare
Namespace Prefix:	caty_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Subordinated debt, prepayment penalty

+ References

No definition available.

+ Details

Name:	caty_SubordinatedDebtPrepaymentPenalty
Namespace Prefix:	caty_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Exercise price per share or per unit of warrants or rights outstanding.

+ References

+ Details

Name:	us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of securities into which the class of warrant or right may be converted. For example, but not limited to, 500,000 warrants may be converted into 1,000,000 shares.

+ References

Reference 1: 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.(i)(2))

-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 08

-Paragraph i

-Subparagraph 2

-Article 4

+ Details

Name:	us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Weighted average interest rate of debt outstanding.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtWeightedAverageInterestRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Interest expense incurred during the reporting period on subordinated notes and debentures. Includes amortization of expenses incurred in the issuance of subordinated notes and debentures.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-04.8)

-URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882

+ Details

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

- Definition

The percentage rate used to calculate dividend payments on preferred stock.

+ References

No definition available.

+ Details

Name:	us-gaap_PreferredStockDividendRatePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Proceeds from issuance of capital stock which provides for a specific dividend that is paid to the shareholders before any dividends to common stockholders and which takes precedence over common stockholders in the event of liquidation.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Financing Activities

-URI http://asc.fasb.org/extlink&oid=6513228

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 14

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3255-108585

+ Details

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

- Definition

Equity impact of the value of stock bought back by the entity at the exercise price or redemption price.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644

+ Details

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

- Definition

Including the current and noncurrent portions, carrying value as of the balance sheet date of subordinated debt (with initial maturities beyond one year or beyond the operating cycle if longer). Subordinated debt places a lender in a lien position behind debt having a higher priority of repayment in liquidation of the entity's assets.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.16)

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 16

-Article 9

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.16)

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 10

-Section F

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Article 5

-Subsection 19, 20, 22

+ Details

Name:	us-gaap_SubordinatedDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Value of outstanding derivative securities that permit the holder the right to purchase securities (usually equity) from the issuer at a specified price.

+ References

Reference 1: 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.(i))

-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 08

-Paragraph i

-Article 4

+ Details

Name:	us-gaap_WarrantsAndRightsOutstanding
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_CreationDateAxis=caty_AfterFiveYearsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreationDateAxis=caty_FirstFiveYearsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByLiabilityClassAxis=us-gaap_SubordinatedDebtObligationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementClassOfStockAxis=us-gaap_SeriesBPreferredStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Note 11 - Capital Resources (Details) (USD $)	0 Months Ended		1 Months Ended	10 Months Ended	12 Months Ended			0 Months Ended	1 Months Ended	21 Months Ended
Note 11 - Capital Resources (Details) (USD $)	Dec. 09, 2013	Dec. 05, 2008	Dec. 31, 2013	Dec. 31, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Sep. 29, 2006	Mar. 31, 2011	Dec. 31, 2012
Note 11 - Capital Resources (Details) [Line Items]
Proceeds from Issuance of Preferred Stock and Preference Stock		$ 258,000,000
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in Shares)		1,846,374
Class of Warrant or Right, Exercise Price of Warrants or Rights (in Dollars per share)		$ 20.96
Warrants and Rights Outstanding		38,700,000us-gaap_WarrantsAndRightsOutstanding
Percent of Senior Preferred Stock Invested		15.00%
Sale of Warrant Consideration Received On Transaction	13,100,000
Sale of Warrants Price Per Share (in Dollars per share)	$ 7.20caty_SaleOfWarrantsPricePerShare
Subordinated Debt								50,000,000us-gaap_SubordinatedDebt
Debt Instrument, Basis Spread on Variable Rate				3.50%
Subordinated Debt Prepayment Penalty			2,000caty_SubordinatedDebtPrepaymentPenalty
Interest Expense, Subordinated Notes and Debentures					4,500,000	3,000,000	3,200,000
Series B Preferred Stock [Member]
Note 11 - Capital Resources (Details) [Line Items]
Proceeds from Issuance of Preferred Stock and Preference Stock		258,000,000
Stock Redeemed or Called During Period, Value						$ 258,000,000
Subordinated Debt Obligations [Member]
Note 11 - Capital Resources (Details) [Line Items]
Debt Instrument, Term								10 years
Debt Instrument, Basis Spread on Variable Rate					1.10%			1.10%	1.10%	3.30%
Debt, Weighted Average Interest Rate							3.61%			3.61%
First Five Years [Member]
Note 11 - Capital Resources (Details) [Line Items]
Preferred Stock, Dividend Rate, Percentage		5.00%
After Five Years [Member]
Note 11 - Capital Resources (Details) [Line Items]
Preferred Stock, Dividend Rate, Percentage		9.00%