Borrowed Funds (Details) (USD $)								9 Months Ended		9 Months Ended				9 Months Ended		1 Months Ended		9 Months Ended
	Sep. 30, 2012	Dec. 31, 2011	Apr. 30, 2012 First American Equipment Finance	Sep. 30, 2012 5.125% Senior Notes Due February 2013 City National Corporation	Dec. 31, 2011 5.125% Senior Notes Due February 2013 City National Corporation	Sep. 30, 2012 5.25% Senior Notes Due September 2020 City National Corporation	Dec. 31, 2011 5.25% Senior Notes Due September 2020 City National Corporation	Sep. 30, 2012 9.00% Subordinated Notes Due July 2019 City National Bank Y	Dec. 31, 2011 9.00% Subordinated Notes Due July 2019 City National Bank	Sep. 30, 2012 9.00% Subordinated Notes Due July 2019 City National Bank LIBOR	Sep. 30, 2012 9.00% Subordinated Notes Due July 2019 City National Bank Prime rate	Sep. 30, 2012 9.00% Subordinated Notes Due August 2019 City National Bank	Dec. 31, 2011 9.00% Subordinated Notes Due August 2019 City National Bank	Sep. 30, 2012 Fixed and Floating Subordinated Notes due August 2019 City National Bank Y	Dec. 31, 2011 Fixed and Floating Subordinated Notes due August 2019 City National Bank	Jun. 30, 2012 5.375% Subordinated Notes Due July 2022 City National Bank	Sep. 30, 2012 5.375% Subordinated Notes Due July 2022 City National Bank	Sep. 30, 2012 Floating Rate Securities Due November 2034 Business Bancorp Capital Trust I	Dec. 31, 2011 Floating Rate Securities Due November 2034 Business Bancorp Capital Trust I	Sep. 30, 2012 Nonrecourse debt	Sep. 30, 2012 Nonrecourse debt First American Equipment Finance
Short-term borrowings
Current portion of senior notes				$ 208,566,000
Federal funds purchased		50,000,000
Total short-term borrowings	211,739,000	50,000,000																		3,173,000
Long-term debt
Long-term debt	706,035,000	697,778,000			215,848,000	297,537,000	297,308,000	49,746,000	49,718,000			74,872,000	74,858,000	54,906,000	54,895,000		148,606,000	5,151,000	5,151,000	75,217,000
Borrowings and nonrecourse debt			320,900,000
Borrowings and nonrecourse debt																					78,400,000
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)																				4.04%
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 (in years)								5						5
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)																		2.40%