Fair Values of Assets and Liabilities - Schedule of Assets Measured on Nonrecurring Basis (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets	$ 962,731	$ 957,719
Fair Value, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	29,785	30,396
Fair Value Measurement Of Assets On Nonrecurring Basis Net Losses On Impaired Loans	(2,667)	(1,778)
Other Real Estate Owned Assets Fair Value	2,608	4,035
Fair Value Measurement Of Assets On Nonrecurring Basis Net Losses On Other Real Estate Owned	(196)	(593)
Total Assets	32,393	34,431
Fair Value Measurement Of Assets On Nonrecurring Basis Net Loss	(2,863)	(2,371)
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets	0	0
Level 1 [Member] | Fair Value, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	0	0
Other Real Estate Owned Assets Fair Value	0	0
Total Assets	0	0
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets	955,266	953,353
Fair Value, Inputs, Level 2 [Member] | Fair Value, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	12,267	15,076
Other Real Estate Owned Assets Fair Value	2,608	4,035
Total Assets	14,875	19,111
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets	7,465	4,366
Level 3 [Member] | Fair Value, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	17,518	15,320
Other Real Estate Owned Assets Fair Value	0	0
Total Assets	$ 17,518	$ 15,320