SECURITIES - Composition of Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Amortized cost (1)
Available-for-sale
Municipal bonds	$ 3,476	$ 15,800
Mortgage-backed securities, U.S. Government agencies and U.S. Government-sponsored enterprises	45,983	53,407
Collateralized mortgage obligations, U.S. Government Agencies	10,462	1,470
Collateralized mortgage obligations, Non-agency	2,271	3,327
SBA bonds	12,278	2,056
CRA mutual funds	851	834
Corporate bonds	3,500	2,000
Preferred stock		7
Total securities available-for-sale	78,821	78,901
Non-marketable securities
Federal Home Loan Bank of Boston stock	3,813	3,211
Gross unrealized gains
Available-for-sale
Municipal bonds	11	197
Mortgage-backed securities, U.S. Government agencies and U.S. Government-sponsored enterprises	152	229
Collateralized mortgage obligations, U.S. Government Agencies	2	4
Collateralized mortgage obligations, Non-agency	410	414
SBA bonds	9	9
CRA mutual funds
Corporate bonds	59	16
Preferred stock		215
Total securities available-for-sale	643	1,084
Non-marketable securities
Federal Home Loan Bank of Boston stock
Gross unrealized losses
Available-for-sale
Municipal bonds	1	1
Mortgage-backed securities, U.S. Government agencies and U.S. Government-sponsored enterprises	267	335
Collateralized mortgage obligations, U.S. Government Agencies	87
Collateralized mortgage obligations, Non-agency	17	6
SBA bonds	20	1
CRA mutual funds	16	16
Corporate bonds	9	3
Preferred stock
Total securities available-for-sale	417	362
Non-marketable securities
Federal Home Loan Bank of Boston stock
Fair value
Available-for-sale
Municipal bonds	3,486	15,996
Mortgage-backed securities, U.S. Government agencies and U.S. Government-sponsored enterprises	45,868	53,301
Collateralized mortgage obligations, U.S. Government Agencies	10,377	1,474
Collateralized mortgage obligations, Non-agency	2,664	3,735
SBA bonds	12,267	2,064
CRA mutual funds	835	818
Corporate bonds	3,550	2,013
Preferred stock		222
Total securities available-for-sale	79,047	79,623
Non-marketable securities
Federal Home Loan Bank of Boston stock	$ 3,813	$ 3,211

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Investments in notes or bonds that are collateralized by a specific group of underlying assets owned by the issuer of the notes or bonds which are short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three-years ago does not become a cash equivalent when its remaining maturity is three months.

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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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The total of collateralized agreements including securities purchased under agreements to resell (repos), borrowed securities, and secured demand notes.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Amount of securities, mortgage loans, or other financial instruments pledged as collateral for deposits.

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Amount of Federal Home Loan Bank (FHLB) and Federal Reserve Bank stock.

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For an unclassified balance sheet, this item represents investments in common and preferred stocks and other forms of securities that provide ownership interests in a corporation.

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Investment in short-term money-market instruments (such as commercial paper, banker's acceptances, repurchase agreements, government securities, certificates of deposit, and so forth) which are highly liquid (that is, readily convertible to known amounts of cash) and so near their maturity that they present an insignificant risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify as cash equivalents by definition. Original maturity means an original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three-years ago does not become a cash equivalent when its remaining maturity is three months.

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Fair value of securitized, pay-through debt securities collateralized by real estate mortgage loans classified as available-for-sale.

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Bonds or similar securities issued by state, city, or local governments or the agencies operated by state, city, or local governments which are short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three-years ago does not become a cash equivalent when its remaining maturity is three months.

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