Allowance for Loan Losses - Summary of Pre and Post-modification Balances for Loans Designated as TDRs (Detail) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2020 USD ($) Loan	Jun. 30, 2019 USD ($) Loan	Jun. 30, 2020 USD ($) Loan	Jun. 30, 2019 USD ($) Loan
Residential First Mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | Loan	[1]	1		1
Pre-Modification Outstanding Recorded Investment	[1]	$ 391		$ 391
Post-Modification Outstanding Recorded Investment	[1]	$ 391		$ 391
Commercial Mortgages (Owner Occupied)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | Loan	[2]		1		1
Pre-Modification Outstanding Recorded Investment	[2]		$ 48		$ 48
Post-Modification Outstanding Recorded Investment	[2]		$ 52		$ 52

[1] Modification was an interest payment deferral.

[2] Modification was an extension of the loan term.