Fair Value Measurements - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Specific adjustments to impaired loans recognized	$ 501,000	$ 79,000
Amortized cost of Level 3 securities	1,635,000	1,635,000
Liabilities measured at fair value on a recurring or nonrecurring basis	0	0
Transfers between level 1, 2 and 3	0	0
Fair Value Measurements, Level 3 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Amortized cost of Level 3 securities	52,276,000	13,301,000
Unrealized loss	$ 0	$ 0