Fair Value of Financial Instruments - Financial Assets Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Total Securities Available-for-Sale	$ 307,812	$ 222,293
Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Total Securities Available-for-Sale		10,021
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		10,021
Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Total Securities Available-for-Sale	306,250	210,782
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	306,250	210,782
Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Total Securities Available-for-Sale	1,562	1,490
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	1,562	1,490
U.S. Treasury [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Total Securities Available-for-Sale		10,021
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		10,021
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	124,241	62,445
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	124,241	62,445
Mortgage-backed Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Total Securities Available-for-Sale	113,056	95,197
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	113,056	95,197
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	70,515	54,630
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	68,953	53,140
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	1,562	1,490
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	$ 1,562	$ 1,490