Loans - Summary of Information Regarding the Credit Quality Indicators for Residential Real Estate and Consumer Loans (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	$ 372,589	$ 333,710
Credit Quality [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	148,249	154,317
Credit Quality [Member] | Residential First Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	108,084	106,120
Credit Quality [Member] | Residential Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	2,097	3,358
Credit Quality [Member] | Consumer Home Equity and Lines of Credit [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	36,154	42,344
Credit Quality [Member] | Consumer Other [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	1,914	2,495
Performing [Member] | Credit Quality [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	147,013	152,753
Performing [Member] | Credit Quality [Member] | Residential First Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	107,018	105,083
Performing [Member] | Credit Quality [Member] | Residential Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	2,097	3,358
Performing [Member] | Credit Quality [Member] | Consumer Home Equity and Lines of Credit [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	35,984	41,819
Performing [Member] | Credit Quality [Member] | Consumer Other [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	1,914	2,493
Non Performing [Member] | Credit Quality [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	1,236	1,564
Non Performing [Member] | Credit Quality [Member] | Residential First Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	1,066	1,037
Non Performing [Member] | Credit Quality [Member] | Consumer Home Equity and Lines of Credit [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	$ 170	525
Non Performing [Member] | Credit Quality [Member] | Consumer Other [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount		$ 2