Borrowed Funds (Details) (USD $)								3 Months Ended		3 Months Ended				3 Months Ended		0 Months Ended			3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012	Mar. 31, 2013 5.125% Senior Notes Due February 2013 City National Corporation	Dec. 31, 2012 5.125% Senior Notes Due February 2013 City National Corporation	Mar. 31, 2013 5.25% Senior Notes Due September 2020 City National Corporation	Dec. 31, 2012 5.25% Senior Notes Due September 2020 City National Corporation	Mar. 31, 2013 9.00% Subordinated Notes Due July 2019 City National Bank	Dec. 31, 2012 9.00% Subordinated Notes Due July 2019 City National Bank	Mar. 31, 2013 9.00% Subordinated Notes Due July 2019 City National Bank LIBOR	Mar. 31, 2013 9.00% Subordinated Notes Due July 2019 City National Bank Prime rate	Mar. 31, 2013 9.00% Subordinated Notes Due August 2019 City National Bank	Dec. 31, 2012 9.00% Subordinated Notes Due August 2019 City National Bank	Mar. 31, 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	Mar. 31, 2013 5.375% Subordinated Notes Due July 2022 City National Bank	Dec. 31, 2012 5.375% Subordinated Notes Due July 2022 City National Bank	Mar. 31, 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	Mar. 31, 2013 Nonrecourse debt	Dec. 31, 2012 Nonrecourse debt
Short-term borrowings
Current portion of senior notes					$ 206,581,000
Federal funds purchased	703,600,000	1,214,200,000
FHLB borrowings	100,000,000
Total short-term borrowings	806,760,000	1,423,798,000	1,423,798,000																		3,160,000	3,017,000
Long-term debt
Long-term debt	702,967,000	706,051,000				297,690,000	297,613,000	49,764,000	49,755,000			74,881,000	74,876,000	54,913,000	54,909,000		148,640,000	148,642,000	5,152,000	5,152,000	71,927,000	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%
Average interest rate (as a percent)																					3.94%
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)																			2.25%