Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Fair Value Measurements (Schedule of Carrying Amounts and Estimated Fair Values of Financial Instruments, Held or Issued for Purposes Other Than Trading) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018
Financial assets:
Cash and cash equivalents	$ 47,444	$ 59,658	$ 38,967	$ 28,613
Available-for-sale debt securities	34,421	41,790
Federal Home Loan Bank of Boston stock	895	1,416
Loans, net	1,341,341	959,286
Accrued interest receivable	6,118	2,854
Financial liabilities:
Deposits	1,168,234	849,905
Borrowings	73,500	24,998
Carrying Amount [Member]
Financial assets:
Cash and cash equivalents	47,444	59,658
Available-for-sale debt securities	34,421	41,790
Federal Home Loan Bank of Boston stock	895	1,416
Loans, net	1,341,341	959,286
Accrued interest receivable	6,118	2,854
Financial liabilities:
Deposits	1,168,234	849,905
Borrowings	73,500	24,998
Fair Value [Member]
Financial assets:
Cash and cash equivalents	47,444	59,658
Available-for-sale debt securities	34,421	41,790
Loans, net	1,352,938	958,270
Accrued interest receivable	6,118	2,854
Financial liabilities:
Deposits	1,168,962	850,774
Borrowings	74,132	25,351
Quoted Prices In Active Markets For Identical Assets Level 1 [Member] \| Fair Value [Member]
Financial assets:
Cash and cash equivalents	47,444	59,658
Significant Other Observable Inputs Level 2 [Member] \| Fair Value [Member]
Financial assets:
Available-for-sale debt securities	34,421	41,790
Accrued interest receivable	6,118	2,854
Financial liabilities:
Deposits	1,168,962	850,774
Borrowings	74,132	25,351
Significant Unobservable Inputs Level 3 [Member] \| Fair Value [Member]
Financial assets:
Loans, net	$ 1,352,938	$ 958,270