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Fair Value Measurements - Quantitative and Qualitative Information (Details) | Dec. 31, 2020 USD ($) | Dec. 31, 2019 USD ($)
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Quantitative information about Level 3 fair value measurements |  |
Mortgage servicing rights, fair value | $ 4,224,000 | $ 5,935,000
Securities available-for-sale, at fair value | 496,178,000 | 484,648,000
Fair Value, Inputs, Level 3 [Member] |  |
Quantitative information about Level 3 fair value measurements |  |
Securities available-for-sale, at fair value | 4,319,000 | 5,419,000
US States and Political Subdivisions Debt Securities [Member] |  |
Quantitative information about Level 3 fair value measurements |  |
Securities available-for-sale, at fair value | 249,259,000 | 249,175,000
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member] |  |
Quantitative information about Level 3 fair value measurements |  |
Securities available-for-sale, at fair value | 4,300,000 | 5,400,000
Collateralized Mortgage Obligations [Member] |  |
Quantitative information about Level 3 fair value measurements |  |
Securities available-for-sale, at fair value | 56,585,000 | 57,984,000
Recurring |  |
Quantitative information about Level 3 fair value measurements |  |
Mortgage servicing rights, fair value | 4,224,000 | 5,935,000
Recurring | Fair Value, Inputs, Level 3 [Member] |  |
Quantitative information about Level 3 fair value measurements |  |
Mortgage servicing rights, fair value | 4,224,000 | 5,935,000
Recurring | US States and Political Subdivisions Debt Securities [Member] |  |
Quantitative information about Level 3 fair value measurements |  |
Securities available-for-sale, at fair value | 249,259,000 | 249,175,000
Recurring | US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member] |  |
Quantitative information about Level 3 fair value measurements |  |
Securities available-for-sale, at fair value | 4,319,000 | 5,419,000
Recurring | Collateralized Mortgage Obligations [Member] |  |
Quantitative information about Level 3 fair value measurements |  |
Securities available-for-sale, at fair value | 56,585,000 | 57,984,000
Recurring | Measurement Input, Discount Rate | Mortgage Servicing Rights [Member] | Discounted Cash Flow | Fair Value, Inputs, Level 3 [Member] |  |
Quantitative information about Level 3 fair value measurements |  |
Mortgage servicing rights, fair value | $ 4,224,000 | $ 5,935,000
Recurring | Measurement Input, Discount Rate | Mortgage Servicing Rights [Member] | Discounted Cash Flow | Fair Value, Inputs, Level 3 [Member] | Minimum [Member] |  |
Quantitative information about Level 3 fair value measurements |  |
Servicing Asset, Measurement Input | 11.0 | 10.0
Recurring | Measurement Input, Discount Rate | Mortgage Servicing Rights [Member] | Discounted Cash Flow | Fair Value, Inputs, Level 3 [Member] | Maximum [Member] |  |
Quantitative information about Level 3 fair value measurements |  |
Servicing Asset, Measurement Input | 15.0 | 58.8
Recurring | Measurement Input, Discount Rate | Mortgage Servicing Rights [Member] | Discounted Cash Flow | Fair Value, Inputs, Level 3 [Member] | Weighted Average [Member] |  |
Quantitative information about Level 3 fair value measurements |  |
Servicing Asset, Measurement Input | 11.0 | 10.1
Recurring | Measurement Input, Constant Prepayment Rate | Mortgage Servicing Rights [Member] | Discounted Cash Flow | Fair Value, Inputs, Level 3 [Member] | Minimum [Member] |  |
Quantitative information about Level 3 fair value measurements |  |
Servicing Asset, Measurement Input | 5.5 | 0.0
Recurring | Measurement Input, Constant Prepayment Rate | Mortgage Servicing Rights [Member] | Discounted Cash Flow | Fair Value, Inputs, Level 3 [Member] | Maximum [Member] |  |
Quantitative information about Level 3 fair value measurements |  |
Servicing Asset, Measurement Input | 59.1 | 69.0
Recurring | Measurement Input, Constant Prepayment Rate | Mortgage Servicing Rights [Member] | Discounted Cash Flow | Fair Value, Inputs, Level 3 [Member] | Weighted Average [Member] |  |
Quantitative information about Level 3 fair value measurements |  |
Servicing Asset, Measurement Input | 19.5 | 14.1

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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. + Details
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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 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(6)) -URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=121558606&loc=SL82898722-210454 Reference 3: 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=121553693&loc=d3e26610-111562 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (aa) -URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27161-111563 + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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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 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6469459&loc=d3e122501-111745 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 860 -SubTopic 50 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6469459&loc=d3e122492-111745 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -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 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 860 -SubTopic 50 -Section 45 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6469459&loc=d3e122501-111745 + Details
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