Allowance for Loan Losses - Performing and Non Performing Loans (Detail) - USD ($) $ in Thousands	Sep. 30, 2015		Dec. 31, 2014
Performing and non performing loans
Loan receivables	$ 187,490		$ 166,016
Performing
Performing and non performing loans
Loan receivables	186,095		165,511
Nonperforming
Performing and non performing loans
Loan receivables	1,395		505
Residential First Mortgages
Performing and non performing loans
Loan receivables	156,004	[1]	135,267	[2]
Residential First Mortgages | Performing
Performing and non performing loans
Loan receivables	154,750	[1]	134,908	[2]
Residential First Mortgages | Nonperforming
Performing and non performing loans
Loan receivables	1,254	[1]	359	[2]
Residential Revolving and Junior Mortgages
Performing and non performing loans
Loan receivables	26,579	[3]	25,400	[4]
Residential Revolving and Junior Mortgages | Performing
Performing and non performing loans
Loan receivables	26,462	[3]	25,369	[4]
Residential Revolving and Junior Mortgages | Nonperforming
Performing and non performing loans
Loan receivables	117	[3]	31	[4]
Consumer and Other Loans
Performing and non performing loans
Loan receivables	4,907	[5]	5,349	[6]
Consumer and Other Loans | Performing
Performing and non performing loans
Loan receivables	4,883	[5]	5,234	[6]
Consumer and Other Loans | Nonperforming
Performing and non performing loans
Loan receivables	$ 24	[5]	$ 115	[6]

[1] Residential First Mortgages which have been assigned a risk rating grade of Substandard totaled $2.2 million as of September 30, 2015.

[2] Residential First Mortgages which have been assigned a risk rating grade of Substandard totaled $2.1 million as of December 31, 2014.

[3] Residential Revolving and Junior Mortgages which have been assigned a risk rating grade of Substandard totaled $15 thousand as of September 30, 2015.

[4] Residential Revolving and Junior Mortgages which have been assigned a risk rating grade of Substandard totaled $219 thousand as of December 31, 2014.

[5] Consumer Loans which have been assigned a risk rating grade of Substandard were $4 thousand as of September 30, 2015.

[6] Consumer Loans which have been assigned a risk rating grade of Substandard totaled $1 thousand as of December 31, 2014.