Loans and Lease Finance Receivables and Allowance for Loan Losses - Summary of Loan, Excluding PCI Loans by Internal Risk Ratings (Detail) - Loans, Excluding PCI Loans [Member] - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial and industrial	$ 479,133	$ 434,099
SBA	111,762	106,867
Commercial real estate, Owner occupied	933,935	838,353
Commercial real estate, Non-owner occupied	1,950,397	1,804,831
Construction, Speculative	54,952	45,837
Construction, Non-speculative	39,057	22,726
SFR mortgage	237,488	233,754
Dairy & livestock and agribusiness	213,830	305,509
Municipal lease finance receivables	71,929	74,135
Consumer and other loans	79,725	69,278
Total gross loans, excluding PCI loans	4,172,208	3,935,389
Pass [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial and industrial	440,455	398,651
SBA	93,259	87,441
Commercial real estate, Owner occupied	827,887	772,114
Commercial real estate, Non-owner occupied	1,909,707	1,741,615
Construction, Speculative	47,301	38,186
Construction, Non-speculative	39,057	22,726
SFR mortgage	229,984	227,207
Dairy & livestock and agribusiness	145,897	285,647
Municipal lease finance receivables	67,188	69,194
Consumer and other loans	75,378	64,844
Total gross loans, excluding PCI loans	3,876,113	3,707,625
Special Mention [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial and industrial	21,264	33,000
SBA	11,697	13,169
Commercial real estate, Owner occupied	87,431	54,758
Commercial real estate, Non-owner occupied	24,804	26,170
Construction, Speculative	0	0
Construction, Non-speculative	0	0
SFR mortgage	4,965	3,556
Dairy & livestock and agribusiness	48,122	19,862
Municipal lease finance receivables	4,741	4,941
Consumer and other loans	1,867	1,618
Total gross loans, excluding PCI loans	204,891	157,074
Substandard [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial and industrial	17,407	2,403
SBA	6,582	4,854
Commercial real estate, Owner occupied	18,617	11,481
Commercial real estate, Non-owner occupied	15,886	37,046
Construction, Speculative	7,651	7,651
Construction, Non-speculative	0	0
SFR mortgage	2,539	2,991
Dairy & livestock and agribusiness	19,811	0
Municipal lease finance receivables	0	0
Consumer and other loans	2,377	2,708
Total gross loans, excluding PCI loans	90,870	69,134
Doubtful & Loss [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial and industrial	7	45
SBA	224	1,403
Commercial real estate, Owner occupied	0	0
Commercial real estate, Non-owner occupied	0	0
Construction, Speculative	0	0
Construction, Non-speculative	0	0
SFR mortgage	0	0
Dairy & livestock and agribusiness	0	0
Municipal lease finance receivables	0	0
Consumer and other loans	103	108
Total gross loans, excluding PCI loans	$ 334	$ 1,556