Loans, Allowance for Loan and Lease Losses, and Reserve for Off-Balance Sheet Credit Commitments (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Accounts notes and loans receivable
Loans and leases, excluding covered loans	$ 17,170,438,000	$ 14,818,295,000
Less: Allowance for loan and lease losses	(302,584,000)	(277,888,000)	(262,557,000)
Loans and leases, excluding covered loans, net	16,867,854,000	14,540,407,000
Covered loans	716,911,000	1,031,004,000
Less: Allowance for loan losses	(15,922,000)	(44,781,000)	(64,565,000)
Covered loans, net	700,989,000	986,223,000
Total loans and leases	17,887,349,000	15,849,299,000
Net loans and leases	17,568,843,000	15,526,630,000
Unamortized fees, net of deferred costs	2,300,000	5,900,000
Aggregate amount of loans to executive officers, directors and companies and individuals affiliated with or guaranteed by officers and directors of the Company and the Bank	122,400,000	87,900,000
New loans and advances made	132,000,000
Repayments of loans and advances	97,500,000
Interest income recognized on loans to executive officers, directors and companies and individuals affiliated with or guaranteed by officers and directors of the Company and the Bank	3,400,000	2,200,000	2,600,000
Past due and nonaccrual loans	0
Imperial Capital Bank
Accounts notes and loans receivable
Covered loans	630,754,000	893,031,000
1st Pacific Bank of California
Accounts notes and loans receivable
Covered loans	40,110,000	70,240,000
Sun West Bank
Accounts notes and loans receivable
Covered loans	18,761,000	34,803,000
Nevada Commerce Bank
Accounts notes and loans receivable
Covered loans	27,286,000	32,930,000
Commercial
Accounts notes and loans receivable
Loans and leases, excluding covered loans	7,404,116,000	6,211,353,000
Covered loans	10,009,000	10,561,000
Commercial | Imperial Capital Bank
Accounts notes and loans receivable
Sharing of recoveries with FDIC on expiration date (as a percent)	80.00%
Sharing of recoveries with FDIC on termination date (as a percent)	80.00%
Commercial | 1st Pacific Bank of California
Accounts notes and loans receivable
Sharing of recoveries with FDIC on expiration date (as a percent)	80.00%
Sharing of recoveries with FDIC on termination date (as a percent)	80.00%
Commercial | Sun West Bank
Accounts notes and loans receivable
Sharing of recoveries with FDIC on expiration date (as a percent)	80.00%
Sharing of recoveries with FDIC on termination date (as a percent)	80.00%
Commercial | Nevada Commerce Bank
Accounts notes and loans receivable
Sharing of recoveries with FDIC on expiration date (as a percent)	80.00%
Sharing of recoveries with FDIC on termination date (as a percent)	80.00%
Commercial real estate mortgages
Accounts notes and loans receivable
Loans and leases, excluding covered loans	3,223,001,000	2,739,284,000
Less: Allowance for loan and lease losses	(50,678,000)	(48,901,000)	(48,451,000)
Covered loans	666,628,000	931,758,000
Residential mortgage
Accounts notes and loans receivable
Loans and leases, excluding covered loans	4,554,311,000	3,962,205,000
Less: Allowance for loan and lease losses	(11,540,000)	(10,558,000)	(14,122,000)
Covered loans	4,976,000	5,652,000
Real estate construction
Accounts notes and loans receivable
Loans and leases, excluding covered loans	367,004,000	313,190,000
Less: Allowance for loan and lease losses	(6,351,000)	(11,784,000)	(20,155,000)
Covered loans	31,184,000	78,554,000
Home equity loans and lines of credit
Accounts notes and loans receivable
Loans and leases, excluding covered loans	709,344,000	711,750,000
Less: Allowance for loan and lease losses	(6,677,000)	(7,283,000)	(8,077,000)
Covered loans	3,695,000	3,790,000
Installment
Accounts notes and loans receivable
Loans and leases, excluding covered loans	151,955,000	142,793,000
Less: Allowance for loan and lease losses	(1,842,000)	(1,858,000)	(1,972,000)
Covered loans	419,000	689,000
Lease financing
Accounts notes and loans receivable
Loans and leases, excluding covered loans	$ 760,707,000	$ 737,720,000