Earnings per Common Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Basic EPS:
Net income attributable to City National Corporation	$ 46,265	$ 39,692
Less: Earnings allocated to participating securities	738	578
Earnings allocated to common shareholders	45,527	39,114
Weighted average common shares outstanding	52,741,000	52,320,000
Basic earnings per common share	$ 0.86	$ 0.75
Diluted EPS:
Earnings allocated to common shareholders	$ 45,530	$ 39,119
Weighted average common shares outstanding	52,741,000	52,320,000
Dilutive effect of equity awards (in shares)	280,000	574,000
Weighted average diluted common shares outstanding	53,021,000	52,894,000
Diluted earnings per common share	$ 0.86	$ 0.74
Average outstanding stock options
Antidilutive securities not included in calculation of diluted EPS:
Antidilutive securities not included in calculation of diluted EPS (in shares)	3,000,000	1,700,000