Fair Value Measurements - Quantitative and Qualitative Information (Details) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Quantitative information about Level 3 fair value measurements
Mortgage servicing rights, fair value	$ 7,357,000	$ 6,944,000
Securities available-for-sale, at fair value	541,248,000	541,439,000
Level 3
Quantitative information about Level 3 fair value measurements
Securities available-for-sale, at fair value	8,165,000	16,529,000
States and political subdivisions
Quantitative information about Level 3 fair value measurements
Securities available-for-sale, at fair value	274,067,000	278,092,000
Collateralized mortgage obligations
Quantitative information about Level 3 fair value measurements
Securities available-for-sale, at fair value	64,429,000	65,939,000
Recurring
Quantitative information about Level 3 fair value measurements
Mortgage servicing rights, fair value	7,357,000	6,944,000
Recurring \| Level 3
Quantitative information about Level 3 fair value measurements
Mortgage servicing rights, fair value	7,357,000	6,944,000
Recurring \| States and political subdivisions
Quantitative information about Level 3 fair value measurements
Securities available-for-sale, at fair value	274,067,000	278,092,000
Recurring \| States and political subdivisions \| Level 3
Quantitative information about Level 3 fair value measurements
Securities available-for-sale, at fair value	8,165,000	14,261,000
Recurring \| Collateralized mortgage obligations
Quantitative information about Level 3 fair value measurements
Securities available-for-sale, at fair value	64,429,000	65,939,000
Recurring \| Collateralized mortgage obligations \| Level 3
Quantitative information about Level 3 fair value measurements
Securities available-for-sale, at fair value		2,268,000
Recurring \| Measurement Input, Discount Rate \| Mortgage servicing rights \| Discounted Cash Flow \| Level 3
Quantitative information about Level 3 fair value measurements
Mortgage servicing rights, fair value	$ 7,357,000	$ 6,944,000
Recurring \| Measurement Input, Discount Rate \| Mortgage servicing rights \| Discounted Cash Flow \| Level 3 \| Minimum
Quantitative information about Level 3 fair value measurements
Servicing Asset, Measurement Input	10.0	10.0
Recurring \| Measurement Input, Discount Rate \| Mortgage servicing rights \| Discounted Cash Flow \| Level 3 \| Maximum
Quantitative information about Level 3 fair value measurements
Servicing Asset, Measurement Input	229.7	34.3
Recurring \| Measurement Input, Discount Rate \| Mortgage servicing rights \| Discounted Cash Flow \| Level 3 \| Weighted Average
Quantitative information about Level 3 fair value measurements
Servicing Asset, Measurement Input	10.2	10.2
Recurring \| Measurement Input, Constant Prepayment Rate \| Mortgage servicing rights \| Discounted Cash Flow \| Level 3 \| Minimum
Quantitative information about Level 3 fair value measurements
Servicing Asset, Measurement Input	7.0	7.0
Recurring \| Measurement Input, Constant Prepayment Rate \| Mortgage servicing rights \| Discounted Cash Flow \| Level 3 \| Maximum
Quantitative information about Level 3 fair value measurements
Servicing Asset, Measurement Input	68.9	68.4
Recurring \| Measurement Input, Constant Prepayment Rate \| Mortgage servicing rights \| Discounted Cash Flow \| Level 3 \| Weighted Average
Quantitative information about Level 3 fair value measurements
Servicing Asset, Measurement Input	9.6	9.6

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

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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.

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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=68078379&loc=d3e122625-111746

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- Definition

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=99377789&loc=d3e19207-110258

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