Summary of Significant Accounting Policies (Details 3) (Restricted stock)	12 Months Ended
Dec. 31, 2011 Y
Restricted stock
Share-based compensation
Vesting period for awards issued under share-based compensation plans (in years)	5

Represents the vesting period of the share-based compensation awards issued under the predecessor plans.

No definition available.

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