Investment securities available for sale - Summary of investment securities available for sale having fair value and unrealized loss position (Details) - USD ($)
Mar. 31, 2021
Dec. 31, 2020
Schedule of Available-for-sale Securities [Line Items]    
Securities in a loss position for less than 12 Months, Fair Value $ 16,712,000 $ 7,222,000
Securities in a loss position for less than 12 Months, Unrealized Losses (521,000) (62,000)
Securities in a loss position for more than 12 Months, Fair Value 1,434,000 2,807,000
Securities in a loss Position for more than 12 Months, Unrealized Losses (75,000) (125,000)
Total Fair Value 18,146,000 10,029,000
Total Unrealized Losses (596,000) (187,000)
Mortgage Backed Securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Securities in a loss position for less than 12 Months, Fair Value 14,218,000 5,475,000
Securities in a loss position for less than 12 Months, Unrealized Losses (428,000) (51,000)
Securities in a loss position for more than 12 Months, Fair Value   0
Securities in a loss Position for more than 12 Months, Unrealized Losses   0
Total Fair Value 14,218,000 5,475,000
Total Unrealized Losses (428,000) (51,000)
Municipals [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Securities in a loss position for less than 12 Months, Fair Value 1,200,000  
Securities in a loss position for less than 12 Months, Unrealized Losses (83,000)  
Total Fair Value 1,200,000  
Total Unrealized Losses (83,000)  
Subordinated Debt Offering [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Securities in a loss position for less than 12 Months, Fair Value 1,294,000 1,747,000
Securities in a loss position for less than 12 Months, Unrealized Losses (10,000) (11,000)
Securities in a loss position for more than 12 Months, Fair Value 1,434,000 2,807,000
Securities in a loss Position for more than 12 Months, Unrealized Losses (75,000) (125,000)
Total Fair Value 2,728,000 4,554,000
Total Unrealized Losses $ (85,000) $ (136,000)