Fair Values of Assets and Liabilities - Schedule of Assets Measured on Nonrecurring Basis (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets	$ 938,309	$ 962,731
Fair Value, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	49,147	29,785
Fair Value Measurement Of Assets On Nonrecurring Basis Net Losses On Impaired Loans	(7,905)	(2,667)
Other Real Estate Owned Assets Fair Value	1,319	2,608
Fair Value Measurement Of Assets On Nonrecurring Basis Net Losses On Other Real Estate Owned	(30)	(196)
Total Assets	50,466	32,393
Fair Value Measurement Of Assets On Nonrecurring Basis Net Loss	(7,935)	(2,863)
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	930,020	955,266
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	35,543	12,267
Other Real Estate Owned Assets Fair Value	1,319	2,608
Total Assets	36,862	14,875
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets	8,289	7,465
Level 3 [Member] | Fair Value, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	13,604	17,518
Other Real Estate Owned Assets Fair Value	0	0
Total Assets	$ 13,604	$ 17,518