Fair Value of Assets and Liabilities - Summary of Carrying Values, Estimated Fair Values and Placement in Fair Value Hierarchy of Company's Financial Instruments (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Financial assets:
Securities available for sale	$ 68,637	$ 62,267
Level 2 [Member]
Financial assets:
Certificates of deposit	3,687	4,711
Securities available for sale	68,637	62,267
Loans held for sale	30,452	2,931
Derivative assets	682	107
Financial liabilities:
Deposits	350,979	309,076
FHLBB advances	38,531	34,971
Derivative liabilities	47
Level 3 [Member]
Financial assets:
Loans, net	331,132	283,542
Carrying Amount [Member]
Financial assets:
Certificates of deposit	3,675	4,675
Securities available for sale	68,637	62,267
Loans held for sale	30,452	2,870
Loans, net	332,991	285,151
Derivative assets	682	107
Financial liabilities:
Deposits	351,179	309,195
FHLBB advances	38,667	34,914
Derivative liabilities	47
Fair Value [Member]
Financial assets:
Certificates of deposit	3,687	4,711
Securities available for sale	68,637	62,267
Loans held for sale	30,452	2,931
Loans, net	331,132	283,542
Derivative assets	682	107
Financial liabilities:
Deposits	350,979	309,076
FHLBB advances	38,531	$ 34,971
Derivative liabilities	$ 47

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

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Fair value portion of deposit liabilities held by the entity, including, but not limited to, foreign and domestic, interest and noninterest bearing, demand deposits, saving deposits, negotiable orders of withdrawal (NOW) and time deposits.

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Fair value portion of borrowing from Federal Home Loan Bank (FHLBank).

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Fair value portion of loans held-for-sale including, but not limited to, mortgage loans and finance receivables.

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Fair value portion of loan receivable, including, but not limited to, mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts.

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