Loans, Allowance for Loan and Lease Losses, and Reserve for Off-Balance Sheet Credit Commitments (Details) (USD $)																	9 Months Ended
	Sep. 30, 2013	Jun. 30, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Dec. 31, 2011	Sep. 30, 2013 Imperial Capital Bank	Dec. 31, 2012 Imperial Capital Bank	Sep. 30, 2013 1st Pacific Bank of California	Dec. 31, 2012 1st Pacific Bank of California	Sep. 30, 2013 Sun West Bank	Dec. 31, 2012 Sun West Bank	Sep. 30, 2013 Nevada Commerce Bank	Dec. 31, 2012 Nevada Commerce Bank	Sep. 30, 2013 Commercial	Dec. 31, 2012 Commercial	Sep. 30, 2013 Commercial Imperial Capital Bank	Sep. 30, 2013 Commercial 1st Pacific Bank of California	Sep. 30, 2013 Commercial Sun West Bank	Sep. 30, 2013 Commercial Nevada Commerce Bank	Sep. 30, 2013 Commercial real estate mortgages	Jun. 30, 2013 Commercial real estate mortgages	Dec. 31, 2012 Commercial real estate mortgages	Sep. 30, 2012 Commercial real estate mortgages	Jun. 30, 2012 Commercial real estate mortgages	Dec. 31, 2011 Commercial real estate mortgages	Sep. 30, 2013 Residential mortgage	Jun. 30, 2013 Residential mortgage	Dec. 31, 2012 Residential mortgage	Sep. 30, 2012 Residential mortgage	Jun. 30, 2012 Residential mortgage	Dec. 31, 2011 Residential mortgage	Sep. 30, 2013 Real estate construction	Jun. 30, 2013 Real estate construction	Dec. 31, 2012 Real estate construction	Sep. 30, 2012 Real estate construction	Jun. 30, 2012 Real estate construction	Dec. 31, 2011 Real estate construction	Sep. 30, 2013 Home equity loans and lines of credit	Jun. 30, 2013 Home equity loans and lines of credit	Dec. 31, 2012 Home equity loans and lines of credit	Sep. 30, 2012 Home equity loans and lines of credit	Jun. 30, 2012 Home equity loans and lines of credit	Dec. 31, 2011 Home equity loans and lines of credit	Sep. 30, 2013 Installment loan	Jun. 30, 2013 Installment loan	Dec. 31, 2012 Installment loan	Sep. 30, 2012 Installment loan	Jun. 30, 2012 Installment loan	Dec. 31, 2011 Installment loan	Sep. 30, 2013 Lease financing	Dec. 31, 2012 Lease financing
Accounts notes and loans receivable
Loans and leases, excluding covered loans	$ 16,566,133,000		$ 14,818,295,000	$ 13,724,651,000											$ 7,126,158,000	$ 6,211,353,000					$ 3,077,183,000		$ 2,739,284,000	$ 2,436,218,000			$ 4,418,231,000		$ 3,962,205,000	$ 3,897,690,000			$ 380,489,000		$ 313,190,000	$ 269,583,000			$ 681,879,000		$ 711,750,000	$ 718,966,000			$ 152,107,000		$ 142,793,000	$ 137,632,000			$ 730,086,000	$ 737,720,000
Less: Allowance for loan and lease losses	(295,947,000)	(289,914,000)	(277,888,000)	(268,440,000)	(269,534,000)	(262,557,000)															(49,926,000)	(53,339,000)	(48,901,000)	(48,176,000)	(49,715,000)	(48,451,000)	(13,114,000)	(8,004,000)	(10,558,000)	(13,282,000)	(12,490,000)	(14,122,000)	(9,691,000)	(8,335,000)	(11,784,000)	(14,017,000)	(14,810,000)	(20,155,000)	(8,298,000)	(5,400,000)	(7,283,000)	(7,671,000)	(7,656,000)	(8,077,000)	(1,872,000)	(1,355,000)	(1,858,000)	(1,914,000)	(1,774,000)	(1,972,000)
Loans and leases, excluding covered loans, net	16,270,186,000		14,540,407,000
Covered loans	780,072,000		1,031,004,000				680,427,000	893,031,000	45,123,000	70,240,000	25,948,000	34,803,000	28,574,000	32,930,000	10,015,000	10,561,000					719,207,000		931,758,000				5,030,000		5,652,000				41,625,000		78,554,000				3,672,000		3,790,000				523,000		689,000
Less: Allowance for loan losses	(25,882,000)	(24,414,000)	(44,781,000)	(44,978,000)	(43,147,000)	(64,565,000)
Covered loans, net	754,190,000		986,223,000
Total loans and leases	17,346,205,000		15,849,299,000
Net loans and leases	17,024,376,000		15,526,630,000
Unamortized fees, net of deferred costs	$ 2,400,000		$ 5,900,000
Sharing of recoveries with FDIC on expiration date (as a percent)																	80.00%	80.00%	80.00%	80.00%
Sharing of recoveries with FDIC on termination date (as a percent)																	80.00%	80.00%	80.00%	80.00%