Fair Value Information - Assets and Liabilities Measured at Fair Value on Non-Recurring Basis (Detail) - Fair Value on Non-Recurring Basis [Member] - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Description of assets
Total assets	$ 938	$ 828
Loans, Excluding PCI Loans [Member] | Asset Held-for-Sale [Member]
Description of assets
Total assets	0	0
Loans, Excluding PCI Loans [Member] | Commercial and Industrial [Member]
Description of assets
Total assets	9,024	251
Loans, Excluding PCI Loans [Member] | Small Business Administration [Member]
Description of assets
Total assets	36	513
Loans, Excluding PCI Loans [Member] | Commercial Real Estate [Member]
Description of assets
Total assets	0	0
Loans, Excluding PCI Loans [Member] | Construction [Member]
Description of assets
Total assets	0	0
Loans, Excluding PCI Loans [Member] | SFR Mortgage [Member]
Description of assets
Total assets	0	0
Loans, Excluding PCI Loans [Member] | Dairy & Livestock and Agribusiness [Member]
Description of assets
Total assets	0	0
Loans, Excluding PCI Loans [Member] | Consumer and Other Loans [Member]
Description of assets
Total assets	0	0
Loans, Excluding PCI Loans [Member] | Other Real Estate Owned [Member]
Description of assets
Total assets	0	64
Level 1 [Member]
Description of assets
Total assets	0	0
Level 1 [Member] | Loans, Excluding PCI Loans [Member] | Asset Held-for-Sale [Member]
Description of assets
Total assets	0	0
Level 1 [Member] | Loans, Excluding PCI Loans [Member] | Commercial and Industrial [Member]
Description of assets
Total assets	0	0
Level 1 [Member] | Loans, Excluding PCI Loans [Member] | Small Business Administration [Member]
Description of assets
Total assets	0	0
Level 1 [Member] | Loans, Excluding PCI Loans [Member] | Commercial Real Estate [Member]
Description of assets
Total assets	0	0
Level 1 [Member] | Loans, Excluding PCI Loans [Member] | Construction [Member]
Description of assets
Total assets	0	0
Level 1 [Member] | Loans, Excluding PCI Loans [Member] | SFR Mortgage [Member]
Description of assets
Total assets	0	0
Level 1 [Member] | Loans, Excluding PCI Loans [Member] | Dairy & Livestock and Agribusiness [Member]
Description of assets
Total assets	0	0
Level 1 [Member] | Loans, Excluding PCI Loans [Member] | Consumer and Other Loans [Member]
Description of assets
Total assets	0	0
Level 1 [Member] | Loans, Excluding PCI Loans [Member] | Other Real Estate Owned [Member]
Description of assets
Total assets	0	0
Level 2 [Member]
Description of assets
Total assets	0	0
Level 2 [Member] | Loans, Excluding PCI Loans [Member] | Asset Held-for-Sale [Member]
Description of assets
Total assets	0	0
Level 2 [Member] | Loans, Excluding PCI Loans [Member] | Commercial and Industrial [Member]
Description of assets
Total assets	0	0
Level 2 [Member] | Loans, Excluding PCI Loans [Member] | Small Business Administration [Member]
Description of assets
Total assets	0	0
Level 2 [Member] | Loans, Excluding PCI Loans [Member] | Commercial Real Estate [Member]
Description of assets
Total assets	0	0
Level 2 [Member] | Loans, Excluding PCI Loans [Member] | Construction [Member]
Description of assets
Total assets	0	0
Level 2 [Member] | Loans, Excluding PCI Loans [Member] | SFR Mortgage [Member]
Description of assets
Total assets	0	0
Level 2 [Member] | Loans, Excluding PCI Loans [Member] | Dairy & Livestock and Agribusiness [Member]
Description of assets
Total assets	0	0
Level 2 [Member] | Loans, Excluding PCI Loans [Member] | Consumer and Other Loans [Member]
Description of assets
Total assets	0	0
Level 2 [Member] | Loans, Excluding PCI Loans [Member] | Other Real Estate Owned [Member]
Description of assets
Total assets	0	0
Level 3 [Member]
Description of assets
Total assets	1,903	1,056
Level 3 [Member] | Loans, Excluding PCI Loans [Member] | Asset Held-for-Sale [Member]
Description of assets
Total assets	0	0
Level 3 [Member] | Loans, Excluding PCI Loans [Member] | Commercial and Industrial [Member]
Description of assets
Total assets	903	253
Level 3 [Member] | Loans, Excluding PCI Loans [Member] | Small Business Administration [Member]
Description of assets
Total assets	1,000	359
Level 3 [Member] | Loans, Excluding PCI Loans [Member] | Commercial Real Estate [Member]
Description of assets
Total assets	0	0
Level 3 [Member] | Loans, Excluding PCI Loans [Member] | Construction [Member]
Description of assets
Total assets	0	0
Level 3 [Member] | Loans, Excluding PCI Loans [Member] | SFR Mortgage [Member]
Description of assets
Total assets	0	0
Level 3 [Member] | Loans, Excluding PCI Loans [Member] | Dairy & Livestock and Agribusiness [Member]
Description of assets
Total assets	0	0
Level 3 [Member] | Loans, Excluding PCI Loans [Member] | Consumer and Other Loans [Member]
Description of assets
Total assets	0	0
Level 3 [Member] | Loans, Excluding PCI Loans [Member] | Other Real Estate Owned [Member]
Description of assets
Total assets	0	444
Carrying Value [Member]
Description of assets
Total assets	1,903	1,056
Carrying Value [Member] | Loans, Excluding PCI Loans [Member] | Asset Held-for-Sale [Member]
Description of assets
Total assets	0	0
Carrying Value [Member] | Loans, Excluding PCI Loans [Member] | Commercial and Industrial [Member]
Description of assets
Total assets	903	253
Carrying Value [Member] | Loans, Excluding PCI Loans [Member] | Small Business Administration [Member]
Description of assets
Total assets	1,000	359
Carrying Value [Member] | Loans, Excluding PCI Loans [Member] | Commercial Real Estate [Member]
Description of assets
Total assets	0	0
Carrying Value [Member] | Loans, Excluding PCI Loans [Member] | Construction [Member]
Description of assets
Total assets	0	0
Carrying Value [Member] | Loans, Excluding PCI Loans [Member] | SFR Mortgage [Member]
Description of assets
Total assets	0	0
Carrying Value [Member] | Loans, Excluding PCI Loans [Member] | Dairy & Livestock and Agribusiness [Member]
Description of assets
Total assets	0	0
Carrying Value [Member] | Loans, Excluding PCI Loans [Member] | Consumer and Other Loans [Member]
Description of assets
Total assets	0	0
Carrying Value [Member] | Loans, Excluding PCI Loans [Member] | Other Real Estate Owned [Member]
Description of assets
Total assets	$ 0	$ 444