Borrowed Funds (Details) (USD $)							6 Months Ended		6 Months Ended				6 Months Ended		0 Months Ended			6 Months Ended
	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2013 5.125% Senior Notes Due February 2013 City National Corporation	Dec. 31, 2012 5.125% Senior Notes Due February 2013 City National Corporation	Jun. 30, 2013 5.25% Senior Notes Due September 2020 City National Corporation	Dec. 31, 2012 5.25% Senior Notes Due September 2020 City National Corporation	Jun. 30, 2013 9.00% Subordinated Notes Due July 2019 City National Bank	Dec. 31, 2012 9.00% Subordinated Notes Due July 2019 City National Bank	Jun. 30, 2013 9.00% Subordinated Notes Due July 2019 City National Bank LIBOR	Jun. 30, 2013 9.00% Subordinated Notes Due July 2019 City National Bank Prime rate	Jun. 30, 2013 9.00% Subordinated Notes Due August 2019 City National Bank	Dec. 31, 2012 9.00% Subordinated Notes Due August 2019 City National Bank	Jun. 30, 2013 Fixed and Floating Subordinated Notes due August 2019 City National Bank	Dec. 31, 2012 Fixed and Floating Subordinated Notes due August 2019 City National Bank	Jun. 20, 2012 5.375% Subordinated Notes Due July 2022 City National Bank	Jun. 30, 2013 5.375% Subordinated Notes Due July 2022 City National Bank	Dec. 31, 2012 5.375% Subordinated Notes Due July 2022 City National Bank	Jun. 30, 2013 Floating Rate Securities Due November 2034 Business Bancorp Capital Trust I	Dec. 31, 2012 Floating Rate Securities Due November 2034 Business Bancorp Capital Trust I	Jun. 30, 2013 Nonrecourse debt	Dec. 31, 2012 Nonrecourse debt
Short-term borrowings
Current portion of senior notes				$ 206,581,000
Federal funds purchased		1,214,200,000
Total short-term borrowings	2,675,000	1,423,798,000																		2,675,000	3,017,000
Long-term debt
Long-term debt	706,537,000	706,051,000			297,766,000	297,613,000	49,774,000	49,755,000			74,886,000	74,876,000	54,916,000	54,909,000		148,677,000	148,642,000	5,152,000	5,152,000	75,366,000	75,104,000
Long-term debt excluding discount and cost of issuance															$ 150,000,000
Fixed interest rate (as a percent)			5.125%	5.125%	5.25%	5.25%	9.00%	9.00%			9.00%	9.00%				5.375%	5.375%
Average interest rate (as a percent)																				3.88%
Variable rate basis									LIBOR	Prime rate			three-month LIBOR					three-month LIBOR
Frequency to reset interest rate													Quarterly					Quarterly
Interest rate cap (as a percent)													10.00%
Interest rate for initial period (as a percent)							9.00%						9.00%
Initial interest rate period							5 years						5 years
Basis spread after initial period (as a percent)									6.00%	5.00%			6.00%
Basis spread (as a percent)																		1.965%
Interest rate as of reporting date (as a percent)																		2.24%