Fair Value of Assets and Liabilities - Fair value hierarchy (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Financial Instruments - Liabilities:
Demand and savings accounts	$ 562,435	$ 489,292
Time deposits	228,640	245,114
Carrying Amount
Financial Instruments - Assets:
Loans receivable	742,179	712,965
Financial Instruments - Liabilities:
Demand and savings accounts	562,435	489,292
Time deposits	228,640	245,114
Long-term borrowings	108,002	99,098
Estimated Fair Value
Financial Instruments - Assets:
Loans receivable	750,957	721,197
Financial Instruments - Liabilities:
Demand and savings accounts	562,435	489,292
Time deposits	234,896	247,456
Long-term borrowings	111,590	100,032
Level 1
Financial Instruments - Liabilities:
Demand and savings accounts	562,435	489,292
Level 3
Financial Instruments - Assets:
Loans receivable	750,957	721,197
Financial Instruments - Liabilities:
Time deposits	234,896	247,456
Long-term borrowings	$ 111,590	$ 100,032