Loans and Lease Finance Receivables and Allowance for Loan Losses - Schedule of Held-for-Investment Loans, Excluding PCI Loans, Individually Evaluated for Impairment by Class of Loans (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment, Total impaired loans	$ 37,764	$ 67,390	$ 63,706
Unpaid Principal Balance, Total impaired loans	44,689	77,899	71,062
Related Allowance, Total impaired loans	630	550	669
Average Recorded Investment, Total impaired loans	37,988	68,110
Interest Income Recognized, Total impaired loans	530	1,427
Recorded Investment, With no related allowance recorded	27,991	58,390	54,757
Unpaid Principal Balance, With no related allowance recorded	34,837	68,815	61,984
Related Allowance, With no related allowance recorded	0	0	0
Average Recorded Investment, With no related allowance recorded	28,779	59,082
Interest Income Recognized, With no related allowance recorded	294	1,231
Recorded Investment, With a related allowance recorded	9,773	9,000	8,949
Unpaid Principal Balance, With a related allowance recorded	9,852	9,084	9,078
Related Allowance, With a related allowance recorded	630	550	669
Average Recorded Investment, With a related allowance recorded	9,209	9,028
Interest Income Recognized, With a related allowance recorded	236	196
Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment, With no related allowance recorded	840	1,097	1,017
Unpaid Principal Balance, With no related allowance recorded	1,727	1,941	1,894
Related Allowance, With no related allowance recorded	0	0	0
Average Recorded Investment, With no related allowance recorded	904	1,172
Interest Income Recognized, With no related allowance recorded	14	15
Recorded Investment, With a related allowance recorded	607	465	626
Unpaid Principal Balance, With a related allowance recorded	668	536	695
Related Allowance, With a related allowance recorded	526	435	626
Average Recorded Investment, With a related allowance recorded	638	478
Interest Income Recognized, With a related allowance recorded	6	1
Small Business Administration [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment, With no related allowance recorded	3,266	3,087	3,207
Unpaid Principal Balance, With no related allowance recorded	4,026	3,688	3,877
Related Allowance, With no related allowance recorded	0	0	0
Average Recorded Investment, With no related allowance recorded	3,347	3,167
Interest Income Recognized, With no related allowance recorded	25	26
Recorded Investment, With a related allowance recorded	232	59	41
Unpaid Principal Balance, With a related allowance recorded	250	59	47
Related Allowance, With a related allowance recorded	42	12	10
Average Recorded Investment, With a related allowance recorded	238	63
Interest Income Recognized, With a related allowance recorded	6	0
Commercial Real Estate Owner Occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment, With no related allowance recorded	4,386	5,987	6,252
Unpaid Principal Balance, With no related allowance recorded	5,573	7,080	7,445
Related Allowance, With no related allowance recorded	0	0	0
Average Recorded Investment, With no related allowance recorded	4,623	5,865
Interest Income Recognized, With no related allowance recorded	87	127
Recorded Investment, With a related allowance recorded	1,000	0	0
Unpaid Principal Balance, With a related allowance recorded	1,000	0	0
Related Allowance, With a related allowance recorded	1	0	0
Average Recorded Investment, With a related allowance recorded	392	0
Interest Income Recognized, With a related allowance recorded	28	0
Commercial Real Estate Non-owner Occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment, With no related allowance recorded	12,522	33,994	34,041
Unpaid Principal Balance, With no related allowance recorded	15,110	39,946	37,177
Related Allowance, With no related allowance recorded	0	0	0
Average Recorded Investment, With no related allowance recorded	12,760	34,567
Interest Income Recognized, With no related allowance recorded	83	838
Recorded Investment, With a related allowance recorded	0	0	0
Unpaid Principal Balance, With a related allowance recorded	0	0	0
Related Allowance, With a related allowance recorded	0	0	0
Average Recorded Investment, With a related allowance recorded	0	0
Interest Income Recognized, With a related allowance recorded	0	0
Construction Speculative [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment, With no related allowance recorded	0	0	0
Unpaid Principal Balance, With no related allowance recorded	0	0	0
Related Allowance, With no related allowance recorded	0	0	0
Average Recorded Investment, With no related allowance recorded	0	0
Interest Income Recognized, With no related allowance recorded	0	0
Recorded Investment, With a related allowance recorded	7,651	7,651	7,651
Unpaid Principal Balance, With a related allowance recorded	7,651	7,651	7,651
Related Allowance, With a related allowance recorded	45	24	13
Average Recorded Investment, With a related allowance recorded	7,651	7,651
Interest Income Recognized, With a related allowance recorded	193	192
Construction Non-speculative [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment, With no related allowance recorded	0	0	0
Unpaid Principal Balance, With no related allowance recorded	0	0	0
Related Allowance, With no related allowance recorded	0	0	0
Average Recorded Investment, With no related allowance recorded	0	0
Interest Income Recognized, With no related allowance recorded	0	0
Recorded Investment, With a related allowance recorded	0	0	0
Unpaid Principal Balance, With a related allowance recorded	0	0	0
Related Allowance, With a related allowance recorded	0	0	0
Average Recorded Investment, With a related allowance recorded	0	0
Interest Income Recognized, With a related allowance recorded	0	0
SFR Mortgage [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment, With no related allowance recorded	5,464	6,228	5,665
Unpaid Principal Balance, With no related allowance recorded	6,331	7,175	6,453
Related Allowance, With no related allowance recorded	0	0	0
Average Recorded Investment, With no related allowance recorded	5,591	6,102
Interest Income Recognized, With no related allowance recorded	60	50
Recorded Investment, With a related allowance recorded	270	816	588
Unpaid Principal Balance, With a related allowance recorded	270	824	640
Related Allowance, With a related allowance recorded	13	77	20
Average Recorded Investment, With a related allowance recorded	277	826
Interest Income Recognized, With a related allowance recorded	3	3
Dairy & Livestock and Agribusiness [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment, With no related allowance recorded	697	7,091	3,685
Unpaid Principal Balance, With no related allowance recorded	697	7,559	3,684
Related Allowance, With no related allowance recorded	0	0	0
Average Recorded Investment, With no related allowance recorded	709	7,269
Interest Income Recognized, With no related allowance recorded	17	167
Recorded Investment, With a related allowance recorded	0	0	0
Unpaid Principal Balance, With a related allowance recorded	0	0	0
Related Allowance, With a related allowance recorded	0	0	0
Average Recorded Investment, With a related allowance recorded	0	0
Interest Income Recognized, With a related allowance recorded	0	0
Municipal Lease Finance Receivables [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment, With no related allowance recorded	0	0	0
Unpaid Principal Balance, With no related allowance recorded	0	0	0
Related Allowance, With no related allowance recorded	0	0	0
Average Recorded Investment, With no related allowance recorded	0	0
Interest Income Recognized, With no related allowance recorded	0	0
Recorded Investment, With a related allowance recorded	0	0	0
Unpaid Principal Balance, With a related allowance recorded	0	0	0
Related Allowance, With a related allowance recorded	0	0	0
Average Recorded Investment, With a related allowance recorded	0	0
Interest Income Recognized, With a related allowance recorded	0	0
Consumer and Other Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment, With no related allowance recorded	816	906	890
Unpaid Principal Balance, With no related allowance recorded	1,373	1,426	1,454
Related Allowance, With no related allowance recorded	0	0	0
Average Recorded Investment, With no related allowance recorded	845	940
Interest Income Recognized, With no related allowance recorded	8	8
Recorded Investment, With a related allowance recorded	13	9	43
Unpaid Principal Balance, With a related allowance recorded	13	14	45
Related Allowance, With a related allowance recorded	3	2	$ 0
Average Recorded Investment, With a related allowance recorded	13	10
Interest Income Recognized, With a related allowance recorded	$ 0	$ 0