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, 2017	Jun. 30, 2016	Dec. 31, 2016
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment, With no related allowance recorded	$ 28,253	$ 27,991	$ 26,018
Recorded Investment, With a related allowance recorded	543	9,773	367
Recorded Investment, Total impaired loans	28,796	37,764	26,385
Unpaid Principal Balance, With no related allowance recorded	33,039	34,837	32,198
Unpaid Principal Balance, With a related allowance recorded	612	9,852	383
Unpaid Principal Balance, Total impaired loans	33,651	44,689	32,581
Related Allowance, With no related allowance recorded		0	0
Related Allowance, With a related allowance recorded	113	630	141
Related Allowance, Total impaired loans	113	630	141
Average Recorded Investment, With no related allowance recorded	28,375	28,779
Average Recorded Investment, With a related allowance recorded	565	9,209
Average Recorded Investment, Total impaired loans	28,940	37,988
Interest Income Recognized, With no related allowance recorded	995	294
Interest Income Recognized, With a related allowance recorded	1	236
Interest Income Recognized, Total impaired loans	996	530
Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment, With no related allowance recorded	1,465	840	730
Recorded Investment, With a related allowance recorded	140	607	171
Unpaid Principal Balance, With no related allowance recorded	1,939	1,727	1,646
Unpaid Principal Balance, With a related allowance recorded	187	668	171
Related Allowance, With no related allowance recorded	0	0	0
Related Allowance, With a related allowance recorded	13	526	114
Average Recorded Investment, With no related allowance recorded	1,572	904
Average Recorded Investment, With a related allowance recorded	157	638
Interest Income Recognized, With no related allowance recorded	13	14
Interest Income Recognized, With a related allowance recorded	1	6
Small Business Administration [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment, With no related allowance recorded	2,472	3,266	3,386
Recorded Investment, With a related allowance recorded	6	232	196
Unpaid Principal Balance, With no related allowance recorded	2,750	4,026	4,189
Unpaid Principal Balance, With a related allowance recorded	23	250	212
Related Allowance, With no related allowance recorded	0	0	0
Related Allowance, With a related allowance recorded	6	42	27
Average Recorded Investment, With no related allowance recorded	2,538	3,347
Average Recorded Investment, With a related allowance recorded	9	238
Interest Income Recognized, With no related allowance recorded	32	25
Interest Income Recognized, With a related allowance recorded	0	6
Commercial Real Estate Owner Occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment, With no related allowance recorded	5,541	4,386	1,797
Recorded Investment, With a related allowance recorded	0	1,000	0
Unpaid Principal Balance, With no related allowance recorded	5,866	5,573	2,276
Unpaid Principal Balance, With a related allowance recorded	0	1,000	0
Related Allowance, With no related allowance recorded	0	0	0
Related Allowance, With a related allowance recorded	0	1	0
Average Recorded Investment, With no related allowance recorded	5,240	4,623
Average Recorded Investment, With a related allowance recorded	0	392
Interest Income Recognized, With no related allowance recorded	69	87
Interest Income Recognized, With a related allowance recorded	0	28
Commercial Real Estate Non-owner Occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment, With no related allowance recorded	13,017	12,522	13,331
Recorded Investment, With a related allowance recorded	0	0	0
Unpaid Principal Balance, With no related allowance recorded	15,469	15,110	15,842
Unpaid Principal Balance, With a related allowance recorded	0	0	0
Related Allowance, With no related allowance recorded	0	0	0
Related Allowance, With a related allowance recorded	0	0	0
Average Recorded Investment, With no related allowance recorded	12,908	12,760
Average Recorded Investment, With a related allowance recorded	0	0
Interest Income Recognized, With no related allowance recorded	798	83
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
Recorded Investment, With a related allowance recorded	0	7,651	0
Unpaid Principal Balance, With no related allowance recorded	0	0	0
Unpaid Principal Balance, With a related allowance recorded	0	7,651	0
Related Allowance, With no related allowance recorded	0	0	0
Related Allowance, With a related allowance recorded	0	45	0
Average Recorded Investment, With no related allowance recorded	0	0
Average Recorded Investment, With a related allowance recorded	0	7,651
Interest Income Recognized, With no related allowance recorded	0	0
Interest Income Recognized, With a related allowance recorded	0	193
Construction Non-speculative [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment, With no related allowance recorded	0	0	0
Recorded Investment, With a related allowance recorded	0	0	0
Unpaid Principal Balance, With no related allowance recorded	0	0	0
Unpaid Principal Balance, With a related allowance recorded	0	0	0
Related Allowance, With no related allowance recorded	0	0	0
Related Allowance, With a related allowance recorded	0	0	0
Average Recorded Investment, With no related allowance recorded	0	0
Average Recorded Investment, With a related allowance recorded	0	0
Interest Income Recognized, With no 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	4,195	5,464	5,174
Recorded Investment, With a related allowance recorded	0	270	0
Unpaid Principal Balance, With no related allowance recorded	4,983	6,331	6,075
Unpaid Principal Balance, With a related allowance recorded	0	270	0
Related Allowance, With no related allowance recorded	0	0	0
Related Allowance, With a related allowance recorded	0	13	0
Average Recorded Investment, With no related allowance recorded	4,242	5,591
Average Recorded Investment, With a related allowance recorded	0	277
Interest Income Recognized, With no related allowance recorded	73	60
Interest Income Recognized, With a related allowance recorded	0	3
Dairy & Livestock and Agribusiness [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded Investment, With no related allowance recorded	829	697	747
Recorded Investment, With a related allowance recorded	0	0	0
Unpaid Principal Balance, With no related allowance recorded	1,091	697	747
Unpaid Principal Balance, With a related allowance recorded	0	0	0
Related Allowance, With no related allowance recorded	0	0	0
Related Allowance, With a related allowance recorded	0	0	0
Average Recorded Investment, With no related allowance recorded	1,123	709
Average Recorded Investment, With a related allowance recorded	0	0
Interest Income Recognized, With no related allowance recorded	1	17
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
Recorded Investment, With a related allowance recorded	0	0	0
Unpaid Principal Balance, With no related allowance recorded	0	0	0
Unpaid Principal Balance, With a related allowance recorded	0	0	0
Related Allowance, With no related allowance recorded	0	0	0
Related Allowance, With a related allowance recorded	0	0	0
Average Recorded Investment, With no related allowance recorded	0	0
Average Recorded Investment, With a related allowance recorded	0	0
Interest Income Recognized, With no 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	734	816	853
Recorded Investment, With a related allowance recorded	397	13	0
Unpaid Principal Balance, With no related allowance recorded	941	1,373	1,423
Unpaid Principal Balance, With a related allowance recorded	402	13	0
Related Allowance, With no related allowance recorded	0	0	0
Related Allowance, With a related allowance recorded	94	3	$ 0
Average Recorded Investment, With no related allowance recorded	752	845
Average Recorded Investment, With a related allowance recorded	399	13
Interest Income Recognized, With no related allowance recorded	9	8
Interest Income Recognized, With a related allowance recorded	$ 0	$ 0