Summary of Significant Accounting Policies (Details)	9 Months Ended
Sep. 30, 2012 entity office
Summary of Significant Accounting Policies
Number of offices for delivery of banking, trust and investment services	78
Number of investment advisory affiliates	5
Number of unconsolidated subsidiary	1
The "more likely than not" threshold must be greater than this percentage (as a percent)	50.00%

The more likely than not threshold must be greater than this percentage to determine whether it is necessary to perform the two-step goodwill impairment test.

No definition available.

Name:	cyn_MoreLikelyThanNotThresholdForGoodwillImpairmentMinimum
Namespace Prefix:	cyn_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration