Sale of Business (Detail) (OneAmerica, USD $)	0 Months Ended
Sep. 02, 2014	Sep. 02, 2014
OneAmerica
Sale of business
Gain of sale of asset	$ 1,200,000
Assets under administration	$ 6,960,000,000	$ 6,960,000,000

Amount of assets that the company holds in a fiduciary capacity or for which it provides non-advisory services.

No definition available.

Name:	cyn_AssetsUnderAdministration
Namespace Prefix:	cyn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant