Earnings per Common Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Basic EPS:
Net income attributable to City National Corporation	$ 68,499	$ 65,461	$ 130,065	$ 119,291
Less: Dividends on preferred stock	4,094	4,094	8,188	8,188
Net income available to common shareholders	64,405	61,367	121,877	111,103
Less: Earnings allocated to participating securities	561	614	1,092	1,153
Earnings allocated to common shareholders	$ 63,844	$ 60,753	$ 120,785	$ 109,950
Weighted-average common shares outstanding	55,748	54,957	55,586	54,824
Basic earnings per common share (in dollars per share)	$ 1.15	$ 1.11	$ 2.17	$ 2.01
Diluted EPS:
Earnings allocated to common shareholders	$ 63,850	$ 60,759	$ 120,797	$ 109,959
Weighted-average common shares outstanding	55,748	54,957	55,586	54,824
Dilutive effect of equity awards (in shares)	915	675	898	717
Weighted-average diluted common shares outstanding	56,663	55,632	56,484	55,541
Diluted earnings per common share (in dollars per share)	$ 1.13	$ 1.09	$ 2.14	$ 1.98
Stock options
Antidilutive securities not included in calculation of diluted EPS:
Antidilutive securities not included in calculation of diluted EPS (in shares)	400	1,100	300	700