Fair Value Measurements - Schedule of estimated fair values and amounts of financial instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Level 1
Financial assets:
Cash and cash equivalents	$ 278,280	$ 220,138
Interest-bearing deposits with financial institutions	1,847	2,420
Federal Reserve Bank of San Francisco and Federal Home Loan Bank stock	7,910	7,910
Loans, net	0	0
Accrued interest receivable	5,653	4,095
Financial liabilities:
Noninterest bearing deposits	661,462	397,000
Interest-bearing deposits	0	0
FHLB borrowings	0	0
Junior subordinated debentures	0	0
Accrued interest payable	227	398
Level 2
Financial assets:
Cash and cash equivalents	0	0
Interest-bearing deposits with financial institutions	0	0
Federal Reserve Bank of San Francisco and Federal Home Loan Bank stock	0	0
Loans, net	0	0
Accrued interest receivable	0	0
Financial liabilities:
Noninterest bearing deposits	0	0
Interest-bearing deposits	748,267	803,549
FHLB borrowings	20,080	29,974
Junior subordinated debentures	17,527	17,527
Accrued interest payable	0	0
Level 3
Financial assets:
Cash and cash equivalents	0	0
Interest-bearing deposits with financial institutions	0	0
Federal Reserve Bank of San Francisco and Federal Home Loan Bank stock	0	0
Loans, net	1,267,639	1,120,096
Accrued interest receivable	0	0
Financial liabilities:
Noninterest bearing deposits	0	0
Interest-bearing deposits	0	0
FHLB borrowings	0	0
Junior subordinated debentures	0	0
Accrued interest payable	0	0
Carrying Value
Financial assets:
Cash and cash equivalents	278,280	220,138
Interest-bearing deposits with financial institutions	1,847	2,420
Federal Reserve Bank of San Francisco and Federal Home Loan Bank stock	7,910	7,910
Loans, net	1,263,367	1,117,511
Accrued interest receivable	5,653	4,095
Financial liabilities:
Noninterest bearing deposits	661,462	397,000
Interest-bearing deposits	746,088	802,570
FHLB borrowings	20,000	30,000
Junior subordinated debentures	17,527	17,527
Accrued interest payable	227	398
Total
Financial assets:
Cash and cash equivalents	278,280	220,138
Interest-bearing deposits with financial institutions	1,847	2,420
Federal Reserve Bank of San Francisco and Federal Home Loan Bank stock	7,910	7,910
Loans, net	1,267,639	1,120,096
Accrued interest receivable	5,653	4,095
Financial liabilities:
Noninterest bearing deposits	661,462	397,000
Interest-bearing deposits	748,267	803,549
FHLB borrowings	20,080	29,974
Junior subordinated debentures	17,527	17,527
Accrued interest payable	$ 227	$ 398