Earnings per Common Share (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Basic EPS:
Net income attributable to City National Corporation	$ 61,566	$ 53,830
Less: Dividends on preferred stock	4,094	4,094
Net income available to common shareholders	57,472	49,736
Less: Earnings allocated to participating securities	529	536
Earnings allocated to common shareholders	56,943	49,200
Weighted-average common shares outstanding	55,422,000	54,689,000
Basic earnings per common share (in dollars per share)	$ 1.03	$ 0.90
Diluted EPS:
Earnings allocated to common shareholders	$ 56,948	$ 49,204
Weighted-average common shares outstanding	55,422,000	54,689,000
Dilutive effect of equity awards (in shares)	884,000	740,000
Weighted-average diluted common shares outstanding	56,306,000	55,429,000
Diluted earnings per common share (in dollars per share)	$ 1.01	$ 0.89
Stock options
Antidilutive securities not included in calculation of diluted EPS:
Antidilutive securities not included in calculation of diluted EPS (in shares)	200,000	400,000