Fair Value Disclosures - Additional Information (Detail)	Jun. 30, 2019 USD ($)		Dec. 31, 2018 USD ($)		Jun. 30, 2018 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans carrying value, recorded investment with allowance	$ 14,701,000		$ 13,793,000		$ 19,633,000
Impaired loans valuation reserves	3,866,000		4,069,000		4,823,000
Impaired loans net fair value	10,835,000
Recorded Investment With No Allowance	11,707,000	[1]	13,741,000	[2]	7,052,000	[3]
Other real estate owned, total	635,000		$ 448,000		$ 642,000
Level 2 Inputs [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans carrying value, recorded investment with allowance	14,701,000
Impaired loans valuation reserves	$ 3,866,000
Minimum [Member] | Measurement Input, Discount Rate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt discounts, percentage	5
Maximum [Member] | Measurement Input, Discount Rate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt discounts, percentage	25

[1] Includes $464,000 of purchased credit impaired loans.

[2] Includes $827,000 of purchased credit impaired loans.

[3] Includes $2,813,000 of purchased credit impaired loans.