Loans (Detail Textuals)	3 Months Ended	12 Months Ended
	Mar. 31, 2018 USD ($) Security Loans	Dec. 31, 2017 USD ($) Security Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans serviced for others	$ 132,100,000	$ 132,400,000
Loans	267,899,000	263,973,000
Total Past Due	312,000	852,000
30-59 Days Past Due And Accruing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	221,000	699,000
90 Days and Over
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	91,000	153,000
Substandard
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	2,316,000	3,193,000
Special Mention
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	1,070,000	116,000
Residential mortgage loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Carrying value of loans pledged as collateral	$ 194,800,000	$ 190,400,000
Number of nonaccrual loans | Security	2	2
Financing receivable, recorded Investment, nonaccrual status	$ 91,000	$ 153,000
Number of loans newly categorized | Loans	2	5
Real estate loans:
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 263,700,000	$ 260,224,000
Total Past Due	312,000	852,000
Real estate loans: | 30-59 Days Past Due And Accruing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	221,000	699,000
Real estate loans: | 90 Days and Over
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	91,000	153,000
Real estate loans: | Substandard
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	2,316,000	3,193,000
Real estate loans: | Special Mention
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	1,070,000	116,000
Real estate loans: | Secured by one-to-four family residences
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	211,265,000	206,894,000
Total Past Due	155,000	852,000
Real estate loans: | Secured by one-to-four family residences | 30-59 Days Past Due And Accruing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	$ 64,000	699,000
Percentage of past due loans decreased	90.80%
Amount of past due loans decreased	$ 635,000
Real estate loans: | Secured by one-to-four family residences | 90 Days and Over
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	91,000	153,000
Real estate loans: | Secured by one-to-four family residences | Substandard
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	2,101,000	2,963,000
Amount of loan decreased	$ 862,000
Percentage of loan decreased	29.10%
Real estate loans: | Secured by one-to-four family residences | Special Mention
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 115,000	116,000
Real estate loans: | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	16,713,000	14,803,000
Total Past Due	0	0
Real estate loans: | Commercial | 30-59 Days Past Due And Accruing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	0	0
Real estate loans: | Commercial | 90 Days and Over
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	0	0
Real estate loans: | Commercial | Substandard
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	0	0
Real estate loans: | Commercial | Special Mention
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	955,000	0
Amount of loan increased		$ 955,000
Number of loans newly categorized | Loans		2
Other Assets
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value of mortgage servicing rights	$ 894,000	$ 892,000