Loans and Lease Finance Receivables and Allowance for Loan Losses - Schedule of Balance and Activity Related to Allowance for Loan Losses for Held-for-Investment Loans by Type (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	$ 59,336	$ 60,709	$ 59,156	$ 59,825
Charge-offs	(25)	(342)	(188)	(686)
Recoveries	1,627	1,187	1,970	2,415
(Recapture of) Provision for Loan Losses	0	(2,000)	0	(2,000)
Ending Balance	60,938	59,554	60,938	59,554
PCI Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	0		0
Charge-offs	0		0
Recoveries	0		0
(Recapture of) Provision for Loan Losses	310		310
Ending Balance	310		310
Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	8,731	7,502	8,588	7,074
Charge-offs	(24)	0	(85)	(134)
Recoveries	141	197	204	232
(Recapture of) Provision for Loan Losses	539	(514)	680	13
Ending Balance	9,387	7,185	9,387	7,185
Small Business Administration [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	1,236	2,196	993	2,557
Charge-offs	0	0	0	(33)
Recoveries	2	3	3	37
(Recapture of) Provision for Loan Losses	(61)	(114)	181	(476)
Ending Balance	1,177	2,085	1,177	2,085
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	38,286	34,848	36,995	33,373
Charge-offs	0	(107)	0	(107)
Recoveries	496	783	635	1,640
(Recapture of) Provision for Loan Losses	1,137	(110)	2,289	508
Ending Balance	39,919	35,414	39,919	35,414
Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	1,151	1,043	2,389	988
Charge-offs	0	0	0	0
Recoveries	875	41	884	50
(Recapture of) Provision for Loan Losses	(798)	(338)	(2,045)	(292)
Ending Balance	1,228	746	1,228	746
SFR Mortgage [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	2,202	2,425	2,103	2,344
Charge-offs	0	(215)	(102)	(215)
Recoveries	0	0	0	185
(Recapture of) Provision for Loan Losses	299	354	500	250
Ending Balance	2,501	2,564	2,501	2,564
Dairy & Livestock and Agribusiness [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	5,176	3,746	6,029	5,479
Charge-offs	0	0	0	0
Recoveries	107	111	206	210
(Recapture of) Provision for Loan Losses	(401)	117	(1,353)	(1,715)
Ending Balance	4,882	3,974	4,882	3,974
Municipal Lease Finance Receivables [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	1,165	1,030	1,153	1,412
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
(Recapture of) Provision for Loan Losses	(50)	(16)	(38)	(398)
Ending Balance	1,115	1,014	1,115	1,014
Consumer and Other Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	1,389	825	906	1,262
Charge-offs	(1)	(20)	(1)	(197)
Recoveries	6	52	38	61
(Recapture of) Provision for Loan Losses	(975)	(23)	(524)	(292)
Ending Balance	419	834	419	834
Unallocated [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	0	7,094	0	5,336
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
(Recapture of) Provision for Loan Losses	0	(1,356)	0	402
Ending Balance	$ 0	$ 5,738	$ 0	$ 5,738