Allowance for Loan Losses - Performing and Non Performing Loans (Detail) - USD ($) $ in Thousands	Jun. 30, 2017		Dec. 31, 2016
Performing and non performing loans
Loan receivables	$ 243,944		$ 223,976
Performing
Performing and non performing loans
Loan receivables	241,098		221,661
Nonperforming
Performing and non performing loans
Loan receivables	2,846		2,315
Residential First Mortgages
Performing and non performing loans
Loan receivables	214,356	[1]	194,007	[2]
Residential First Mortgages | Performing
Performing and non performing loans
Loan receivables	212,467	[1]	191,852	[2]
Residential First Mortgages | Nonperforming
Performing and non performing loans
Loan receivables	1,889	[1]	2,155	[2]
Residential Revolving and Junior Mortgages
Performing and non performing loans
Loan receivables	26,299	[3]	26,425	[4]
Residential Revolving and Junior Mortgages | Performing
Performing and non performing loans
Loan receivables	25,342	[3]	26,265	[4]
Residential Revolving and Junior Mortgages | Nonperforming
Performing and non performing loans
Loan receivables	957	[3]	160	[4]
Consumer and Other Loans
Performing and non performing loans
Loan receivables	3,289	[5]	3,544	[6]
Consumer and Other Loans | Performing
Performing and non performing loans
Loan receivables	$ 3,289	[5]	$ 3,544	[6]

[1] Residential First Mortgages which have been assigned a risk rating grade of Substandard totaled $2.3 million as of June 30, 2017.

[2] Residential First Mortgages which have been assigned a risk rating grade of Substandard totaled $3.3 million as of December 31, 2016.

[3] Residential Revolving and Junior Mortgages which have been assigned a risk rating grade of Substandard totaled $1.0 million as of June 30, 2017.

[4] Residential Revolving and Junior Mortgages which have been assigned a risk rating grade of Substandard totaled $1.1 million as of December 31, 2016.

[5] Consumer Loans had been assigned a risk rating grade of Substandard as of June 30, 2017 totaled $85 thousand as of June 30, 2017.

[6] No Consumer Loans had been assigned a risk rating grade of Substandard as of December 31, 2016