Investment Securities - Summary of Amortized Cost and Estimated Market Value of Investment Securities by Contractual Maturity (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Available-for-sale Securities, Debt Maturities [Abstract]
Amortized Cost, due in one year or less	$ 25
Amortized Cost, due after one year through five years	12,480
Amortized Cost, due after five years through ten years	12,452
Amortized Cost, due after ten years	19,234
Amortized Cost	44,191	$ 48,614
Market Value, due in one year or less	25
Market Value, due after one year through five years	12,946
Market Value, due after five years through ten years	13,221
Market Value, due after ten years	19,799
Market Value, total	$ 45,991	$ 48,998

Amortized cost 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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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in sixth through tenth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Fair value of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in sixth through tenth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in second through fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Fair value of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in second through fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Fair value of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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