Composition of Securities - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Available-for-sale
CRA mutual fund		$ 882
Debt Securities, Available-for-sale, Cost of Security Sold or Transferred, Method, Specific Identification [Member]
Available-for-sale
U.S. Government Agency notes		4,520
Municipal bonds		26,562
U.S. Government agencies and U.S. Government- sponsored enterprises		28,961
U.S. Government agencies		25,041
Corporate bonds		5,000
Total securities available-for-sale		90,084
Non-marketable securities
Federal Home Loan Bank of Boston stock		3,242
AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Parent [Member]
Available-for-sale
U.S. Government Agency notes		125
Municipal bonds		704
U.S. Government agencies and U.S. Government- sponsored enterprises		420
U.S. Government agencies		468
Corporate bonds		108
Total securities available-for-sale		1,825
Non-marketable securities
Federal Home Loan Bank of Boston stock
Accumulated Net Unrealized Investment Gain Loss 1 [Member]
Available-for-sale
U.S. Government Agency notes		1
Municipal bonds		73
U.S. Government agencies and U.S. Government- sponsored enterprises		24
U.S. Government agencies		10
Corporate bonds
Total securities available-for-sale		108
Non-marketable securities
Federal Home Loan Bank of Boston stock
Securities Financing Transaction, Fair Value [Member]
Available-for-sale
U.S. Government Agency notes		4,644
Municipal bonds		27,193
U.S. Government agencies and U.S. Government- sponsored enterprises		29,357
U.S. Government agencies		25,499
Corporate bonds		5,108
Total securities available-for-sale		91,801
CRA mutual fund		882
Non-marketable securities
Federal Home Loan Bank of Boston stock		$ 3,242
Debt Securities, Available-for-sale, Cost of Security Sold or Transferred, Method, Specific Identification [Member]
Available-for-sale
U.S. Government Agency notes	$ 5,643
Municipal bonds	25,219
U.S. Government agencies and U.S. Government- sponsored enterprises	35,256
U.S. Government agencies	18,439
Corporate bonds	7,750
Total securities available-for-sale	92,307
Non-marketable securities
Federal Home Loan Bank of Boston stock	3,158
AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Parent [Member]
Available-for-sale
U.S. Government Agency notes	176
Municipal bonds	1,348
U.S. Government agencies and U.S. Government- sponsored enterprises	1,288
U.S. Government agencies	598
Corporate bonds	101
Total securities available-for-sale	3,511
Non-marketable securities
Federal Home Loan Bank of Boston stock
Accumulated Net Unrealized Investment Gain Loss 1 [Member]
Available-for-sale
U.S. Government Agency notes	32
Municipal bonds	9
U.S. Government agencies and U.S. Government- sponsored enterprises	36
U.S. Government agencies
Corporate bonds	21
Total securities available-for-sale	98
Non-marketable securities
Federal Home Loan Bank of Boston stock
Securities Financing Transaction, Fair Value [Member]
Available-for-sale
U.S. Government Agency notes	5,787
Municipal bonds	26,558
U.S. Government agencies and U.S. Government- sponsored enterprises	36,508
U.S. Government agencies	19,037
Corporate bonds	7,830
Total securities available-for-sale	95,720
CRA mutual fund	916
Non-marketable securities
Federal Home Loan Bank of Boston stock	$ 3,158