Name:	cyn_FinancingReceivableModificationsIncreaseInRecordedInvestment
Namespace Prefix:	cyn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Represents the decrease in the amount of outstanding recorded investment related to financing receivables that have been modified by troubled debt restructurings due to the removal of loans that are no longer reported as TDRs.

No definition available.

Name:	cyn_FinancingReceivableModificationsNonreportableTDR
Namespace Prefix:	cyn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Amount of specific reserves related to financing receivables that have been modified by troubled debt restructurings within the previous 12 months, for which there was a payment default during the reporting period.

No definition available.

Name:	cyn_FinancingReceivableModificationSubsequentDefaultSpecificReserves
Namespace Prefix:	cyn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	cyn_FinancingReceivableTroubledDebtRestructuringsAbstract
Namespace Prefix:	cyn_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Represents the number of notes into which an original note is separated.

No definition available.

Name:	cyn_NumberOfNotesIntoWhichOriginalNoteSeparated
Namespace Prefix:	cyn_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Number of financing receivables that have been modified by troubled debt restructurings within the previous 12 months and for which there was a payment default.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 34

-URI http://asc.fasb.org/extlink&oid=28368275&loc=SL6953682-111524

Name:	us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Amount of investment related to financing receivables modified by troubled debt restructurings within the previous 12 months, for which there was a payment default.

Name:	us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Reflects the unfunded portion of contractual agreements to lend funds to borrowers for loans whose terms have been modified by troubled debt restructuring.

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