Fair Value of Financial Instruments - Financial Assets Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Total Securities Available-for-Sale	$ 352,974	$ 307,812
Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Total Securities Available-for-Sale	43,325
Level 1 [Member] | Fair Value on a Recurring Basis [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Total Securities Available-for-Sale	43,325
Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Total Securities Available-for-Sale	308,110	306,250
Level 2 [Member] | Fair Value on a Recurring Basis [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Total Securities Available-for-Sale	308,110	306,250
Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Total Securities Available-for-Sale	1,539	1,562
Level 3 [Member] | Fair Value on a Recurring Basis [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Total Securities Available-for-Sale	1,539	1,562
U.S. Treasury [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Total Securities Available-for-Sale	43,325
U.S. Treasury [Member] | Level 1 [Member] | Fair Value on a Recurring Basis [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Total Securities Available-for-Sale	43,325
U.S. Government Agencies [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Total Securities Available-for-Sale	130,799	124,241
U.S. Government Agencies [Member] | Level 2 [Member] | Fair Value on a Recurring Basis [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Total Securities Available-for-Sale	130,799	124,241
Mortgage-backed Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Total Securities Available-for-Sale	116,363	113,056
Mortgage-backed Securities [Member] | Level 2 [Member] | Fair Value on a Recurring Basis [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Total Securities Available-for-Sale	116,363	113,056
State and Local Governments [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Total Securities Available-for-Sale	62,487	70,515
State and Local Governments [Member] | Level 2 [Member] | Fair Value on a Recurring Basis [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Total Securities Available-for-Sale	60,948	68,953
State and Local Governments [Member] | Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Total Securities Available-for-Sale	1,539	1,562
State and Local Governments [Member] | Level 3 [Member] | Fair Value on a Recurring Basis [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Total Securities Available-for-Sale	$ 1,539	$ 1,562