Fair Value - Assets Measured at Fair Value on a Non-Recurring Basis (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other Real Estate	$ 24,000		$ 24,000		$ 1,200,000
Real Estate Owned, Valuation Allowance, Component	23,000		23,000		261,000
Fair Value, Other real estate owned	1,000		1,000
Other Real Estate Owned Write Downs	1,000	$ 227,000	27,000	$ 301,000
Nonrecurring [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value, Other real estate owned					916,000
Nonrecurring [Member] | One-to-four family residential real estate loans [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value, Other real estate owned					102,000
Nonrecurring [Member] | Nonresidential real estate loans [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value, Other real estate owned					814,000
Nonrecurring [Member] | Land Loans [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value, Other real estate owned	1,000		1,000
Nonrecurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value, Other real estate owned					0
Nonrecurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | One-to-four family residential real estate loans [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value, Other real estate owned					0
Nonrecurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Nonresidential real estate loans [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value, Other real estate owned					0
Nonrecurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Land Loans [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value, Other real estate owned	0		0
Nonrecurring [Member] | Significant Observable Inputs (Level 2) [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value, Other real estate owned					0
Nonrecurring [Member] | Significant Observable Inputs (Level 2) [Member] | One-to-four family residential real estate loans [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value, Other real estate owned					0
Nonrecurring [Member] | Significant Observable Inputs (Level 2) [Member] | Nonresidential real estate loans [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value, Other real estate owned					0
Nonrecurring [Member] | Significant Observable Inputs (Level 2) [Member] | Land Loans [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value, Other real estate owned	0		0
Nonrecurring [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value, Other real estate owned	1,000		1,000		916,000
Nonrecurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Nonresidential Real Estate [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other Real Estate					814,000
Nonrecurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | One-to-four family residential real estate loans [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other Real Estate					102,000
Nonrecurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Land Loans [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value, Other real estate owned	$ 1,000		$ 1,000
Sales Comparison Valuation Technique [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other Real Estate					$ 916,000
Impaired Loans [Member] | Sales Comparison Valuation Technique [Member] | Nonresidential real estate loans [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Real estate owned, measurement input					0.056
Impaired Loans [Member] | Sales Comparison Valuation Technique [Member] | Land Loans [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Real estate owned, measurement input	0.123		0.123
Measurement Input, Comparability Adjustment [Member] | Maximum [Member] | Real Estate Properties [Domain] | Nonresidential Real Estate [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Real estate owned, measurement input					0.1522
Measurement Input, Comparability Adjustment [Member] | Minimum [Member] | Real Estate Properties [Domain] | Nonresidential Real Estate [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Real estate owned, measurement input					(0.0366)
Measurement Input, Comparability Adjustment [Member] | Weighted Average [Member] | Real Estate Properties [Domain] | Nonresidential Real Estate [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Real estate owned, measurement input					0.1100