Borrowed Funds (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Short-term borrowings
Total short-term borrowings	$ 6,490	$ 322,861
Long-term debt
Long-term debt	650,078	638,600
5.25% Senior Notes Due September 2020 | City National Corporation
Long-term debt
Long-term debt	$ 299,597	$ 299,540
Fixed interest rate (as a percent)	5.25%	5.25%
9.00% Subordinated Notes Due August 2019 | City National Bank:
Long-term debt
Long-term debt	$ 75,000	$ 75,000
Fixed interest rate (as a percent)	9.00%	9.00%
5.375% Subordinated Notes Due July 2022 | City National Bank:
Long-term debt
Long-term debt	$ 149,995	$ 149,994
Fixed interest rate (as a percent)	5.375%	5.375%
Floating Rate Securities Due November 2034 | Business Bancorp Capital Trust I
Long-term debt
Long-term debt	$ 5,155	$ 5,155
Variable rate basis	three-month LIBOR
Basis spread (as a percent)	1.965%
Interest rate as of reporting date (as a percent)	2.29%
Nonrecourse debt
Short-term borrowings
Current portion of nonrecourse debt	$ 6,490	2,861
Long-term debt
Long-term debt	$ 110,713	99,139
Average interest rate (as a percent)	3.83%
Other long-term debt
Long-term debt
Long-term debt	$ 9,618	9,772
Fixed interest rate (as a percent)	5.64%
Federal funds purchased
Short-term borrowings
Federal funds purchased		$ 320,000