Fair Value Measurement - Assets and Liabilities Measured at Fair Value (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total securities available for sale	$ 365,886	$ 358,499
Equity securities	803	1,191
Assets	0	0
(Level 2) [Member] | Assets Measured at Fair Value on a Recurring Basis [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total securities available for sale	365,886	358,499
Equity securities	803	1,191
(Level 2) [Member] | Assets Measured at Fair Value on a Recurring Basis [Member] | Swap [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Swap asset	23,003	8,918
Swap liability	23,003	8,918
(Level 2) [Member] | Assets Measured at Fair Value on a Recurring Basis [Member] | U.S. Treasury Securities and Obligations of U.S. Government Agencies [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total securities available for sale	19,611	19,601
(Level 2) [Member] | Assets Measured at Fair Value on a Recurring Basis [Member] | Obligations of States and Political Subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total securities available for sale	212,149	206,034
(Level 2) [Member] | Assets Measured at Fair Value on a Recurring Basis [Member] | Mortgage-backed Securities in Government Sponsored Entities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total securities available for sale	134,126	132,864
(Level 3) [Member] | Assets Measured at Fair Value on a Nonrecurring Basis [Member] | Impaired Loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	$ 1	$ 1