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Fair Value Measurements - Quantitative and Qualitative Information (Details)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Quantitative information about Level 3 fair value measurements
Mortgage servicing rights, fair value	$ 5,935,000	$ 7,357,000
Securities available-for-sale, at fair value	484,648,000	541,248,000
Level 3
Quantitative information about Level 3 fair value measurements
Securities available-for-sale, at fair value	5,419,000	8,165,000
US States and Political Subdivisions Debt Securities [Member]
Quantitative information about Level 3 fair value measurements
Securities available-for-sale, at fair value	249,175,000	274,067,000
Collateralized Mortgage Obligations [Member]
Quantitative information about Level 3 fair value measurements
Securities available-for-sale, at fair value	57,984,000	64,429,000
Recurring
Quantitative information about Level 3 fair value measurements
Mortgage servicing rights, fair value	5,935,000	7,357,000
Recurring | Level 3
Quantitative information about Level 3 fair value measurements
Mortgage servicing rights, fair value	5,935,000	7,357,000
Recurring | US States and Political Subdivisions Debt Securities [Member]
Quantitative information about Level 3 fair value measurements
Securities available-for-sale, at fair value	249,175,000	274,067,000
Recurring | US States and Political Subdivisions Debt Securities [Member] | Level 3
Quantitative information about Level 3 fair value measurements
Securities available-for-sale, at fair value	5,419,000	8,165,000
Recurring | Collateralized Mortgage Obligations [Member]
Quantitative information about Level 3 fair value measurements
Securities available-for-sale, at fair value	57,984,000	64,429,000
Recurring | Measurement Input, Discount Rate | Mortgage Servicing Rights [Member] | Discounted Cash Flow | Level 3
Quantitative information about Level 3 fair value measurements
Mortgage servicing rights, fair value	$ 5,935,000	$ 7,357,000
Recurring | Measurement Input, Discount Rate | Mortgage Servicing Rights [Member] | Discounted Cash Flow | Level 3 | Minimum [Member]
Quantitative information about Level 3 fair value measurements
Servicing Asset, Measurement Input	10.0	10.0
Recurring | Measurement Input, Discount Rate | Mortgage Servicing Rights [Member] | Discounted Cash Flow | Level 3 | Maximum [Member]
Quantitative information about Level 3 fair value measurements
Servicing Asset, Measurement Input	58.8	229.7
Recurring | Measurement Input, Discount Rate | Mortgage Servicing Rights [Member] | Discounted Cash Flow | Level 3 | Weighted Average [Member]
Quantitative information about Level 3 fair value measurements
Servicing Asset, Measurement Input	10.1	10.2
Recurring | Measurement Input, Constant Prepayment Rate | Mortgage Servicing Rights [Member] | Discounted Cash Flow | Level 3 | Minimum [Member]
Quantitative information about Level 3 fair value measurements
Servicing Asset, Measurement Input	0.0	7.0
Recurring | Measurement Input, Constant Prepayment Rate | Mortgage Servicing Rights [Member] | Discounted Cash Flow | Level 3 | Maximum [Member]
Quantitative information about Level 3 fair value measurements
Servicing Asset, Measurement Input	69.0	68.9
Recurring | Measurement Input, Constant Prepayment Rate | Mortgage Servicing Rights [Member] | Discounted Cash Flow | Level 3 | Weighted Average [Member]
Quantitative information about Level 3 fair value measurements
Servicing Asset, Measurement Input	14.1	9.6

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- Definition

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

+ References

No definition available.

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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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-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=116651436&loc=d3e122625-111746

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Value of input used to measure servicing asset.

+ 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=117815213&loc=d3e19207-110258

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