Loans and Lease Finance Receivables and Allowance for Loan Losses - Schedule of Recorded Investment in, and Aging of, Past Due and Nonaccrual Loans, Excluding PCI Loans by Class of Loans (Detail) - USD ($)	Jun. 30, 2016	Dec. 31, 2015
30-59 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual	$ 84,000	$ 456,000
60-89 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual	338,000	9,100,000
Loans, Excluding PCI Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due and Accruing	478,000	1,436,000
Nonaccrual	17,472,000	21,019,000
Current	4,154,258,000	3,912,934,000
Total gross loans, excluding PCI loans	4,172,208,000	3,935,389,000
Loans, Excluding PCI Loans [Member] | 30-59 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due and Accruing	478,000	1,436,000
Loans, Excluding PCI Loans [Member] | 60-89 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due and Accruing	0	0
Loans, Excluding PCI Loans [Member] | Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due and Accruing	61,000	0
Nonaccrual	568,000	704,000
Current	478,504,000	433,395,000
Total gross loans, excluding PCI loans	479,133,000	434,099,000
Loans, Excluding PCI Loans [Member] | Commercial and Industrial [Member] | 30-59 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due and Accruing	61,000	0
Loans, Excluding PCI Loans [Member] | Commercial and Industrial [Member] | 60-89 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due and Accruing	0	0
Loans, Excluding PCI Loans [Member] | Small Business Administration [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due and Accruing	0	0
Nonaccrual	2,637,000	2,567,000
Current	109,125,000	104,300,000
Total gross loans, excluding PCI loans	111,762,000	106,867,000
Loans, Excluding PCI Loans [Member] | Small Business Administration [Member] | 30-59 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due and Accruing	0	0
Loans, Excluding PCI Loans [Member] | Small Business Administration [Member] | 60-89 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due and Accruing	0	0
Loans, Excluding PCI Loans [Member] | Commercial Real Estate Owner Occupied [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due and Accruing	0	0
Nonaccrual	1,759,000	4,174,000
Current	932,176,000	834,179,000
Total gross loans, excluding PCI loans	933,935,000	838,353,000
Loans, Excluding PCI Loans [Member] | Commercial Real Estate Owner Occupied [Member] | 30-59 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due and Accruing	0	0
Loans, Excluding PCI Loans [Member] | Commercial Real Estate Owner Occupied [Member] | 60-89 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due and Accruing	0	0
Loans, Excluding PCI Loans [Member] | Commercial Real Estate Non-owner Occupied [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due and Accruing	320,000	354,000
Nonaccrual	9,637,000	10,367,000
Current	1,940,440,000	1,794,110,000
Total gross loans, excluding PCI loans	1,950,397,000	1,804,831,000
Loans, Excluding PCI Loans [Member] | Commercial Real Estate Non-owner Occupied [Member] | 30-59 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due and Accruing	320,000	354,000
Loans, Excluding PCI Loans [Member] | Commercial Real Estate Non-owner Occupied [Member] | 60-89 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due and Accruing	0	0
Loans, Excluding PCI Loans [Member] | Construction Speculative [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due and Accruing	0	0
Nonaccrual	0	0
Current	54,952,000	45,837,000
Total gross loans, excluding PCI loans	54,952,000	45,837,000
Loans, Excluding PCI Loans [Member] | Construction Speculative [Member] | 30-59 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due and Accruing	0	0
Loans, Excluding PCI Loans [Member] | Construction Speculative [Member] | 60-89 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due and Accruing	0	0
Loans, Excluding PCI Loans [Member] | Construction Non-speculative [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due and Accruing	0	0
Nonaccrual	0	0
Current	39,057,000	22,726,000
Total gross loans, excluding PCI loans	39,057,000	22,726,000
Loans, Excluding PCI Loans [Member] | Construction Non-speculative [Member] | 30-59 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due and Accruing	0	0
Loans, Excluding PCI Loans [Member] | Construction Non-speculative [Member] | 60-89 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due and Accruing	0	0
Loans, Excluding PCI Loans [Member] | SFR Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due and Accruing	0	1,082,000
Nonaccrual	2,443,000	2,688,000
Current	235,045,000	229,984,000
Total gross loans, excluding PCI loans	237,488,000	233,754,000
Loans, Excluding PCI Loans [Member] | SFR Mortgage [Member] | 30-59 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due and Accruing	0	1,082,000
Loans, Excluding PCI Loans [Member] | SFR Mortgage [Member] | 60-89 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due and Accruing	0	0
Loans, Excluding PCI Loans [Member] | Dairy & Livestock and Agribusiness [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due and Accruing	0	0
Nonaccrual	0	0
Current	213,830,000	305,509,000
Total gross loans, excluding PCI loans	213,830,000	305,509,000
Loans, Excluding PCI Loans [Member] | Dairy & Livestock and Agribusiness [Member] | 30-59 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due and Accruing	0	0
Loans, Excluding PCI Loans [Member] | Dairy & Livestock and Agribusiness [Member] | 60-89 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due and Accruing	0	0
Loans, Excluding PCI Loans [Member] | Municipal Lease Finance Receivables [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due and Accruing	0	0
Nonaccrual	0	0
Current	71,929,000	74,135,000
Total gross loans, excluding PCI loans	71,929,000	74,135,000
Loans, Excluding PCI Loans [Member] | Municipal Lease Finance Receivables [Member] | 30-59 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due and Accruing	0	0
Loans, Excluding PCI Loans [Member] | Municipal Lease Finance Receivables [Member] | 60-89 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due and Accruing	0	0
Loans, Excluding PCI Loans [Member] | Consumer and Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due and Accruing	97,000	0
Nonaccrual	428,000	519,000
Current	79,200,000	68,759,000
Total gross loans, excluding PCI loans	79,725,000	69,278,000
Loans, Excluding PCI Loans [Member] | Consumer and Other Loans [Member] | 30-59 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due and Accruing	97,000	0
Loans, Excluding PCI Loans [Member] | Consumer and Other Loans [Member] | 60-89 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due and Accruing	$ 0	$ 0