Accrued interest rate on deferred bonus.

No definition available.

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- Definition

Represents the amount of deferred bonus accrued in other liabilities.

+ References

No definition available.

+ Details

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- Definition

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

+ References

No definition available.

+ Details

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- Definition

Represents federal home loan bank prepaid advances.

+ References

No definition available.

+ Details

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- Definition

Floating Interest Rate, Range of Time Period

+ References

No definition available.

+ Details

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- Definition

Investment securities pledged as collateral.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

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

- Definition

Number Of Fixed-To-Floating Security Sold Under Agreements To Repurchase

+ References

No definition available.

+ Details

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Data Type:	xbrli:positiveIntegerItemType
Balance Type:	na
Period Type:	instant

- Definition

Number Of Floating-To-Fixed Rate Agreements

+ References

No definition available.

+ Details

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Namespace Prefix:	caty_
Data Type:	xbrli:integerItemType
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- Definition

Prepaid Security Sold Under Repurchase Agreement

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
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Period Type:	instant

- Definition

Prepayment Penalty Security Sold Under Agreements To Repurchase

+ References

No definition available.

+ Details

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

- Definition

No authoritative reference available.

+ References

No definition available.

+ Details

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- Definition

Represents the threshold for deferred bonus.

+ References

No definition available.

+ Details

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- Definition

Total Fixed To Floating Rate Agreements

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
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- Definition

Total Floating To Fixed Rate

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Represents the weighted average rate for prepaying federal home loan bank advances.

+ References

No definition available.

+ Details

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

- Definition

Weighted Average Rate Of Securities Sold Under Agreements

+ References

No definition available.

+ Details

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Period Type:	instant

- Definition

Carrying value as of the balance sheet date of obligations incurred and payable for incentive compensation awarded to employees and directors or earned by them based on the terms of one or more relevant arrangements.

+ References

+ Details

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Balance Type:	credit
Period Type:	instant

- Definition

Amount of borrowings as of the balance sheet date from the Federal Home Loan Bank, which are primarily used to cover shortages in the required reserve balance and liquidity shortages.

+ References

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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

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

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22(a)(1))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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- Definition

Minimum contractual interest rate for funds borrowed, under the debt agreement.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

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

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-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22(a)(2))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- Definition

Describes the weighted average interest rate applicable to the specific advances from the Federal Home Loan Bank, by branch, as of the Balance Sheet date.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 470

-Section 45

-Paragraph 1

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-Paragraph 1

-Subparagraph (SX 210.5-02.19(b))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- Definition

Interest expense on all other items not previously classified. For example, includes dividends associated with redeemable preferred stock of a subsidiary that is treated as a liability in the parent's consolidated balance sheet.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4D

-URI http://asc.fasb.org/extlink&oid=35706170&loc=SL5624177-113959

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-Topic 942

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph -4

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- Definition

Amount of income earned, after hedging basis adjustments, from fees charged for prepayment of certain Federal Home Loan Bank (FHLBank) advances before original maturity.

+ References

No definition available.

+ Details

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- Definition

Amount, after the effects of master netting arrangements, of funds outstanding borrowed in the form of a security repurchase agreement between the entity and another party for the sale and repurchase of identical or substantially the same securities at a date certain for a specified price. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.13(1))

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-Topic 235

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.4-08.(m)(1)(a)(i))

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

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- Details

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Note 10 - Borrowed Funds (Details) (USD $)	1 Months Ended	10 Months Ended	12 Months Ended
Note 10 - Borrowed Funds (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2005	Dec. 31, 2004
Note 10 - Borrowed Funds (Details) [Line Items]
Securities Sold under Agreements to Repurchase	$ 450,000,000	$ 450,000,000	$ 450,000,000	$ 800,000,000
Weighted Average Rate Of Securities Sold Under Agreements	3.85%	3.85%	3.85%	3.87%
Prepaid Security Sold Under Repurchase Agreement	100,000,000	100,000,000	100,000,000	450,000,000
Rate of Prepaid Security Sold Under Repurchase Agreements	3.50%	3.50%	3.50%	3.79%
Prepayment Penalty Security Sold Under Agreements to Repurchase	3,400,000	3,400,000	3,400,000	22,600,000
Debt Instrument, Basis Spread on Variable Rate		3.50%
Debt Instrument, Interest Rate, Stated Percentage	8.00%	8.00%	8.00%
Advances from Federal Home Loan Banks	425,000,000	425,000,000	425,000,000	521,200,000
Federal Home Loan Bank, Advances, Branch of FHLB Bank, Weighted Average Interest Rate	0.32%	0.32%	0.32%	0.17%
Federal Home Loan Bank Prepaid Advances			171,200,000caty_FederalHomeLoanBankPrepaidAdvances	0caty_FederalHomeLoanBankPrepaidAdvances
Weighted Average Rate for Prepaying Federal Home Loan Bank Advances	1.08%	1.08%	1.08%
Prepayment Fees on Advances, Net			527,000us-gaap_PrepaymentFeesOnAdvancesNet	0us-gaap_PrepaymentFeesOnAdvancesNet
Threshold for Deferred Bonus						225,000caty_ThresholdForDeferredBonus
Amount of Deferred Bonus Accrued in Other Liabilities			300,000				610,000
Accrued Interest on Deferred Bonus	5.06%caty_AccruedInterestOnDeferredBonus	5.02%caty_AccruedInterestOnDeferredBonus					7.00%caty_AccruedInterestOnDeferredBonus
Debt Instrument Basis Spread on Variable Rate 2	2.75%	2.75%	2.75%
Interest Expense, Other			93,000us-gaap_InterestExpenseOther	77,000us-gaap_InterestExpenseOther	71,000us-gaap_InterestExpenseOther
Accrued Bonuses	1,500,000	1,500,000	1,500,000	1,100,000
Callable Securities [Member]
Note 10 - Borrowed Funds (Details) [Line Items]
Securities Sold under Agreements to Repurchase	250,000,000	250,000,000	250,000,000
Floating to Fixed Rate Agreements Totaling $200 Million [Member] \| London Interbank Offered Rate (LIBOR) [Member] \| Maximum [Member]
Note 10 - Borrowed Funds (Details) [Line Items]
Debt Instrument, Basis Spread on Variable Rate			3.40%
Floating to Fixed Rate Agreements Totaling $200 Million [Member] \| Maximum [Member]
Note 10 - Borrowed Funds (Details) [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.07%	5.07%	5.07%
Floating to Fixed Rate Agreements Totaling $200 Million [Member] \| Minimum [Member]
Note 10 - Borrowed Funds (Details) [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.89%	4.89%	4.89%
Floating to Fixed Rate Agreements Totaling $200 Million [Member]
Note 10 - Borrowed Funds (Details) [Line Items]
Number of Floating-to-fixed Rate Agreements	4	4	4
Total Floating to Fixed Rate	200,000,000	200,000,000	200,000,000
Floating Interest Rate, Range of Time Period			1 year
Floating to Fixed Rate Agreement Totaling $50 Million [Member]
Note 10 - Borrowed Funds (Details) [Line Items]
Floating Interest Rate, Range of Time Period			9 months
Debt Instrument, Interest Rate, Stated Percentage	1.00%	1.00%	1.00%
Number of Fixed-to-floating Security Sold Under Agreements to Repurchase	1	1	1
Total Fixed to Floating Rate Agreements	50,000,000	50,000,000	50,000,000
Securities Sold under Agreements to Repurchase [Member]
Note 10 - Borrowed Funds (Details) [Line Items]
Investment Securities Pledged As Collateral	$ 516,300,000	$ 516,300,000	$ 516,300,000	$ 906,100,000
London Interbank Offered Rate (LIBOR) [Member] \| Minimum [Member]
Note 10 - Borrowed Funds (Details) [Line Items]
Debt Instrument, Basis Spread on Variable Rate			3.50%
London Interbank Offered Rate (LIBOR) [Member]
Note 10 - Borrowed Funds (Details) [Line Items]
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Minimum			0.00%