Fair Value Measurement - Assets and Liabilities Measured at Fair Value on Nonrecurring Basis (Detail) - USD ($) $ in Thousands	6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Foreclosed assets (Residential real estate)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value			$ 417
Individually evaluated loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	$ 162		1,055
Fair Value Nonrecurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value		$ 1,618	1,472
Total Gains/(Losses)		(871)	(679)
Fair Value Nonrecurring Basis | Foreclosed assets (Residential real estate)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value			417
Total Gains/(Losses)			(27)
Fair Value Nonrecurring Basis | Individually evaluated loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	162	1,164	1,055
Total Gains/(Losses)	(16)	(808)	(652)
Fair Value Nonrecurring Basis | Foreclosed Assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value		454
Total Gains/(Losses)		(63)
Fair Value Nonrecurring Basis | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value		0	0
Fair Value Nonrecurring Basis | Level 1 | Foreclosed assets (Residential real estate)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value			0
Fair Value Nonrecurring Basis | Level 1 | Individually evaluated loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	0	0	0
Fair Value Nonrecurring Basis | Level 1 | Foreclosed Assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value		0
Fair Value Nonrecurring Basis | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value		0	0
Fair Value Nonrecurring Basis | Level 2 | Foreclosed assets (Residential real estate)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value			0
Fair Value Nonrecurring Basis | Level 2 | Individually evaluated loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	0	0	0
Fair Value Nonrecurring Basis | Level 2 | Foreclosed Assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value		0
Fair Value Nonrecurring Basis | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value		1,618	1,472
Fair Value Nonrecurring Basis | Level 3 | Foreclosed assets (Residential real estate)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value			417
Fair Value Nonrecurring Basis | Level 3 | Individually evaluated loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	$ 162	1,164	$ 1,055
Fair Value Nonrecurring Basis | Level 3 | Foreclosed Assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value		$ 454