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

Represents the amount of recorded investment related to financing receivables that have been removed from troubled debt restructuring status due to charge-off.

No definition available.

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

Represents the amount of recorded investment related to financing receivables that have been removed from troubled debt restructuring status due to payment received.

No definition available.

Name:	cyn_FinancingReceivableModificationsRecordedInvestmentReceivedPayments
Namespace Prefix:	cyn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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 during the reporting period.

No definition available.

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

Amount of outstanding recorded investment 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_FinancingReceivableModificationSubsequentDefaultRecordedInvestment
Namespace Prefix:	cyn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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.