Represents the fair value of covered loans that an Entity acquires in an acquisition. Covered loans are loans subject to a loss share agreement with the Federal Deposit Insurance Corporation.

Name:	cyn_AcquisitionCoveredLoans
Namespace Prefix:	cyn
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Represents the fair value of covered other real estate owned that an Entity acquires in an acquisition. Covered other real estate owned are other real estate owned subject to a loss share agreement with the Federal Deposit Insurance Corporation.

+ Details

Name:	cyn_AcquisitionCoveredOtherRealEstateOwned
Namespace Prefix:	cyn
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Represents the fair value of deposits that an Entity assumes in an acquisition.

+ Details

Name:	cyn_AcquisitionDeposits
Namespace Prefix:	cyn
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Represents the additional gain due to the revision in the first loss tranche under the FDIC loss-sharing agreement.

+ Details

Name:	cyn_AdditionalGainOnFirstLossTrancheRevised
Namespace Prefix:	cyn
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Carrying value of assets acquired in the business acquisition.

+ Details

Name:	cyn_BusinessAcquisitionCarryingValueOfAssetsAcquired
Namespace Prefix:	cyn
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Carrying value of liabilities assumed in the business acquisition.

+ Details

Name:	cyn_BusinessAcquisitionCarryingValueOfLiabilitiesAssumed
Namespace Prefix:	cyn
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Fair value of intangible assets representing the value of the entity's long-term relationships with depositors, commonly known as core deposit intangibles, which are separate from the financial instruments themselves, assumed in a business combination.

+ Details

Name:	cyn_BusinessAcquisitionCoreDepositIntangibleAssumed
Namespace Prefix:	cyn
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The fair value of customer contract intangibles acquired in business acquisition.

+ Details

Name:	cyn_BusinessAcquisitionCustomerContractIntangible
Namespace Prefix:	cyn
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Fair value of goodwill acquired in the business acquisition.

+ Details

Name:	cyn_BusinessAcquisitionGoodwillAcquired
Namespace Prefix:	cyn
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Represents cash received from the FDIC for the net settlement of a business combination.

+ Details

Name:	cyn_CashReceivedFromFDIC
Namespace Prefix:	cyn
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Represents the expected reimbursement from the Federal Deposit Insurance Corporation related to expected losses on acquired loans, other real estate owned, and unfunded loan commitments.

+ Details

Name:	cyn_FDICIndemnificationAsset
Namespace Prefix:	cyn
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Represents an entity's estimated liability to the FDIC at acquisition date should actual cumulative losses on acquired covered assets be lower than the cumulative losses originally estimated by the FDIC.

+ Details

Name:	cyn_FDICLossSharingLiability
Namespace Prefix:	cyn
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Represents the percentage of eligible loss that will be reimbursed by Federal Deposit Insurance Corporation ("FDIC") as per loss-sharing agreement between the entity and FDIC.

+ Details

Name:	cyn_LossSharingAgreementPercentageOfReimbursementFromFDIC
Namespace Prefix:	cyn
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the period for which the loss-sharing agreements is applicable for all loans, excluding single family residential loans, expressed in number of years.

+ Details

Name:	cyn_TermOfAgreementForOtherLoans
Namespace Prefix:	cyn
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the period for which the loss-sharing agreements is applicable for single family residential loans expressed in number of years.

+ Details

Name:	cyn_TermOfAgreementForSingleFamilyResidentialLoans
Namespace Prefix:	cyn
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of cash paid to acquire the entity.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141

-Paragraph 51

-Subparagraph d

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141R

-Paragraph 68

-Subparagraph f(1)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Name:	us-gaap_BusinessAcquisitionCostOfAcquiredEntityCashPaid
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ Details

Name:	us-gaap_BusinessAcquisitionLineItems
Namespace Prefix:	us-gaap
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141R

-Paragraph 59

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 10

-Section 25

-Paragraph 23

-URI http://asc.fasb.org/extlink&oid=6909708&loc=d3e1043-128460

+ Details

Name:	us-gaap_BusinessCombinationAcquisitionRelatedCosts
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of the excess of the fair value of acquired net assets over the cost of an acquired business after pro rata reduction of the amounts that otherwise would have been assigned to acquired assets except financial assets other than investments accounted for by the equity method, assets to be disposed of by sale, deferred tax assets, prepaid assets relating to pension and postretirement benefit plans, and other current assets. This amount is considered an extraordinary item and often referred to as negative goodwill. This element is gross of the related tax effect.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141

-Paragraph 44, 45, 46

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Name:	us-gaap_GainOnPurchaseOfBusiness
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Business Combinations (Details) (USD $)	3 Months Ended	9 Months Ended			1 Months Ended	3 Months Ended				3 Months Ended			3 Months Ended
Business Combinations (Details) (USD $)	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Dec. 31, 2010	Apr. 30, 2011 Nevada Commerce Bank	Sep. 30, 2011 Nevada Commerce Bank Y	Apr. 08, 2011 Nevada Commerce Bank	Feb. 11, 2011 Branch office in San Jose	Nov. 15, 2010 Datafaction Inc.	Sep. 30, 2011 Sun West Bank and 1st Pacific Bank of California Y	Jun. 30, 2010 Sun West Bank	May 28, 2010 Sun West Bank	Sep. 30, 2010 1st Pacific Bank of California	Jun. 30, 2010 1st Pacific Bank of California	May 07, 2010 1st Pacific Bank of California
Business acquisitions
Deposits	$ (541,499,000)	$ (126,795,000)	$ (541,499,000)				$ 118,400,000	$ 8,400,000				$ 304,300,000			$ 237,200,000
Acquired goodwill								300,000	6,200,000
Core deposit intangible								100,000
Customer contract intangible									2,200,000
Carrying value of assets acquired							138,900,000					340,000,000			318,600,000
Carrying value of liabilities assumed							121,900,000					310,100,000			264,200,000
Covered loans	330,566,000	55,313,000	330,566,000				56,400,000					127,600,000			202,800,000
Covered other real estate owned	15,161,000	7,463,000	15,161,000				7,500,000					12,100,000
Cash paid on acquisition															12,300,000
Cash from the FDIC							2,700,000					29,200,000
FDIC reimbursement (as a percent)						80.00%				80.00%
Term of loss-sharing agreements for single family residential loans (in years)						10				10
Term of loss-sharing agreements for other loans (in years)						8				8
FDIC indemnification asset	324,240,000	212,809,000	324,240,000	295,466,000			33,800,000					104,600,000			36,500,000
FDIC liability															3,600,000
FDIC gain	2,111,000	8,164,000	27,339,000		8,200,000						24,700,000			500,000
Additional gain on first loss tranche													2,100,000
Acquisition related expense					$ 300,000