Nature of Operations and Basis of Presentation - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2016 Segment shares	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Cash equivalents maturity period	90 days
Time period to capture relevant loan loss data	48 months
Obligation to repurchase mortgage loans prescribed time period	4 months
Description of tax benefit	A tax position is recognized as a benefit if it is “more likely than not” that the tax position would be sustained in a tax examination, with a tax examination being presumed to occur. The amount recognized is the largest amount of tax benefit greater than 50% likely of being realized on examination. For tax positions not meeting the “more likely than not” test, no tax benefit is recorded.
Uncertain tax positions		$ 0	$ 0
Interest or penalties		0	0
Defined benefit plan, unrecognized net actuarial loss			$ 344,000
Defined benefit plan, prior service credits		89,000
Defined benefit plan, net actuarial losses		$ 38,000
Number of operating segment | Segment	1
Common stock equivalents, outstanding | shares	0
Consumer Loans or Second Mortgages and HELOCs [Member]
Summary Of Significant Accounting Policies [Line Items]
Impairment disclosure requirement	Unless such loans are 90 days past due or are subject to a troubled debt restructuring agreement.
Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Certificates of deposit maturity period	1 year
Percentage of tax benefit that likely of being realized on examination with taxing authority	50.00%
Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Certificates of deposit maturity period	5 years
Maximum [Member] | Residential One-to-Four Family Real Estate Portfolio Segment [Member]
Summary Of Significant Accounting Policies [Line Items]
Loan-to-value ratio	80.00%
Maximum [Member] | Second Mortgages and Home Equity Lines of Credit Property Segment [Member]
Summary Of Significant Accounting Policies [Line Items]
Loan-to-value ratio	80.00%