Loan and Lease Finance Receivables and Allowance for Credit Losses - Summary of Allowance for Credit Losses and Recorded Investment in Held-For-Investment Loans by Portfolio Segment (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses, Beginning balance	$ 92,441	$ 93,964
Allowance for loan losses, Charge-offs	(546)	(2,356)
Allowance for loan losses, Recoveries	323	314
Allowance for loan losses, Ending balance	92,218	91,922
Allowance for loan losses, Individually evaluated for impairment	4,071	1,510
Allowance for loan losses, Collectively evaluated for impairment	88,147	90,412
Ending balance, March 31, 2013	3,375,695	3,433,459
Individually evaluated for impairment	112,721	97,186
Collectively evaluated for impairment	3,084,280	3,094,330
Acquired loans with deteriorated credit quality, net of discount	178,694	241,943
Covered Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses, Charge-offs		(31)
Allowance for loan losses, Provision / reallocation of ALLL		31
Ending balance, March 31, 2013	178,694	241,943
Acquired loans with deteriorated credit quality, net of discount	178,694	241,943
Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses, Beginning balance	11,652	10,654
Allowance for loan losses, Charge-offs	(357)	(560)
Allowance for loan losses, Recoveries	99	62
Allowance for loan losses, Provision / reallocation of ALLL	919	1,751
Allowance for loan losses, Ending balance	12,313	11,907
Allowance for loan losses, Individually evaluated for impairment	1,055	421
Allowance for loan losses, Collectively evaluated for impairment	11,258	11,486
Ending balance, March 31, 2013	532,941	497,625
Individually evaluated for impairment	4,579	7,820
Collectively evaluated for impairment	528,362	489,805
Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses, Beginning balance	2,291	4,947
Allowance for loan losses, Recoveries	126	27
Allowance for loan losses, Provision / reallocation of ALLL	(293)	(651)
Allowance for loan losses, Ending balance	2,124	4,323
Allowance for loan losses, Collectively evaluated for impairment	2,124	4,323
Ending balance, March 31, 2013	55,703	67,382
Individually evaluated for impairment	27,491	29,354
Collectively evaluated for impairment	28,212	38,028
Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses, Beginning balance	50,905	51,873
Allowance for loan losses, Charge-offs	(142)	(530)
Allowance for loan losses, Recoveries	71	221
Allowance for loan losses, Provision / reallocation of ALLL	(503)	371
Allowance for loan losses, Ending balance	50,331	51,935
Allowance for loan losses, Individually evaluated for impairment	429	787
Allowance for loan losses, Collectively evaluated for impairment	49,902	51,148
Ending balance, March 31, 2013	2,158,220	2,153,345
Individually evaluated for impairment	55,098	51,153
Collectively evaluated for impairment	2,103,122	2,102,192
Municipal Lease Finance Receivables [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses, Beginning balance	1,588	2,403
Allowance for loan losses, Provision / reallocation of ALLL	1,044	(383)
Allowance for loan losses, Ending balance	2,632	2,020
Allowance for loan losses, Collectively evaluated for impairment	2,632	2,020
Ending balance, March 31, 2013	109,727	114,724
Collectively evaluated for impairment	109,727	114,724
Dairy and Livestock / Agribusiness [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses, Beginning balance	18,696	17,278
Allowance for loan losses, Charge-offs		(1,150)
Allowance for loan losses, Recoveries	14
Allowance for loan losses, Provision / reallocation of ALLL	(2,139)	(48)
Allowance for loan losses, Ending balance	16,571	16,080
Allowance for loan losses, Individually evaluated for impairment	2,560	221
Allowance for loan losses, Collectively evaluated for impairment	14,011	15,859
Ending balance, March 31, 2013	283,872	290,578
Individually evaluated for impairment	25,327	8,470
Collectively evaluated for impairment	258,545	282,108
Consumer, Auto & Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses, Beginning balance	1,170	1,590
Allowance for loan losses, Charge-offs	(47)	(85)
Allowance for loan losses, Recoveries	13	4
Allowance for loan losses, Provision / reallocation of ALLL	(3)	(20)
Allowance for loan losses, Ending balance	1,133	1,489
Allowance for loan losses, Individually evaluated for impairment	27	81
Allowance for loan losses, Collectively evaluated for impairment	1,106	1,408
Ending balance, March 31, 2013	56,538	67,862
Individually evaluated for impairment	226	389
Collectively evaluated for impairment	56,312	67,473
Unallocated [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses, Beginning balance	6,139	5,219
Allowance for loan losses, Provision / reallocation of ALLL	975	(1,051)
Allowance for loan losses, Ending balance	7,114	4,168
Allowance for loan losses, Collectively evaluated for impairment	$ 7,114	$ 4,168