Fair Value - Level 3 Fair Value Measurements for Financial Instruments on a Non-recurring Basis (Details) $ in Thousands	12 Months Ended
Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale	$ 88,179	$ 93,383
Fair Value, Other real estate owned	0	900
Fair value of mortgage servicing rights	$ 420	513
Other Real Estate Owned [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Other real estate owned		$ 916
One to Four Family Residential Real Estate Loans [Member] \| Sales comparison [Member] \| Other Real Estate Owned [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements, Valuation Processes, Description		Sales comparison
Fair Value Measurements, Sensitivity Analysis, Description		Discount applied to valuation
Nonresidential real estate loans [Member] \| Sales comparison [Member] \| Other Real Estate Owned [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements, Valuation Processes, Description		Sales comparison
Fair Value Measurements, Sensitivity Analysis, Description		Comparison between sales and income approaches
Land [Member] \| Sales comparison [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements, Valuation Processes, Description	Sales comparison
Fair Value Measurements, Sensitivity Analysis, Description	Discount applied to valuation
Land [Member] \| Sales comparison [Member] \| Impaired Loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Real Estate Owned, Measurement Input	0.123
Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale	$ 88,179	$ 93,383
Fair Value, Other real estate owned		916
Fair Value, Measurements, Nonrecurring [Member] \| One to Four Family Residential Real Estate Loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Other real estate owned		102
Fair Value, Measurements, Nonrecurring [Member] \| Nonresidential real estate loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Impaired loans	270
Fair Value, Other real estate owned		814
Fair Value, Measurements, Nonrecurring [Member] \| Land [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Other real estate owned	1
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale	0	0
Fair Value, Other real estate owned		916
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Measurements, Nonrecurring [Member] \| One to Four Family Residential Real Estate Loans [Member] \| Other Real Estate Owned [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Other real estate owned		102
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Measurements, Nonrecurring [Member] \| Nonresidential real estate loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Impaired loans	270
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Measurements, Nonrecurring [Member] \| Nonresidential real estate loans [Member] \| Other Real Estate Owned [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Other real estate owned		$ 814
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Measurements, Nonrecurring [Member] \| Land [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Other real estate owned	$ 1
Measurement Input, Discount Rate [Member] \| One to Four Family Residential Real Estate Loans [Member] \| Sales comparison [Member] \| Weighted Average [Member] \| Other Real Estate Owned [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Real Estate Owned, Measurement Input	0.0560
Measurement Input, Comparability Adjustment [Member] \| Nonresidential real estate loans [Member] \| Sales comparison [Member] \| Minimum [Member] \| Other Real Estate Owned [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Real Estate Owned, Measurement Input	0.1522
Measurement Input, Comparability Adjustment [Member] \| Nonresidential real estate loans [Member] \| Sales comparison [Member] \| Maximum [Member] \| Other Real Estate Owned [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Real Estate Owned, Measurement Input	(0.0366)
Measurement Input, Comparability Adjustment [Member] \| Nonresidential real estate loans [Member] \| Sales comparison [Member] \| Weighted Average [Member] \| Other Real Estate Owned [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Real Estate Owned, Measurement Input	(0.1100)

Impaired loan fair value.

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- Definition

Real estate acquired through foreclosure fair value.

+ References

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- Definition

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109979856&loc=d3e26610-111562

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-Topic 320
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-Section 50
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-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

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+ References

No definition available.

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Description of the sensitivity of the fair value measurements to changes in unobservable inputs and the inter-relationships between those inputs as well as how those inter-relationships might magnify or mitigate the effect of changes in the unobservable inputs on the fair value measurements.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
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Description of the valuation processes in place for fair value measurements categorized within Level 3 of the fair value hierarchy.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (f)
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- Definition

Value of input used to measure real estate owned by financial institution by financial institution which is not directly related to its business.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258

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- Definition

Fair value of an asset representing net future revenue from contractually specified servicing fees, late charges, and other ancillary revenues, in excess of future costs related to servicing arrangements.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6469459&loc=d3e122501-111745

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-Paragraph 3
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-URI http://asc.fasb.org/extlink&oid=68078379&loc=d3e122625-111746

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