Fair Value Measurements - Quantitative and Qualitative Information (Details) $ in Thousands	Sep. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)
Quantitative information about Level 3 fair value measurements
Mortgage servicing rights, fair value	$ 5,010	$ 5,935
Securities available-for-sale, at fair value	448,421	484,648
Level 3
Quantitative information about Level 3 fair value measurements
Mortgage servicing rights, fair value	5,010	5,935
Securities available-for-sale, at fair value	4,790	5,419
US States and Political Subdivisions Debt Securities [Member]
Quantitative information about Level 3 fair value measurements
Securities available-for-sale, at fair value	249,777	249,175
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	4,800	5,900
Collateralized Mortgage Obligations [Member]
Quantitative information about Level 3 fair value measurements
Securities available-for-sale, at fair value	$ 57,013	$ 57,984
Measurement Input, Discount Rate | Mortgage Servicing Rights [Member] | Level 3 | Minimum [Member]
Quantitative information about Level 3 fair value measurements
Servicing Asset, Measurement Input	11.0	10.0
Measurement Input, Discount Rate | Mortgage Servicing Rights [Member] | Level 3 | Maximum [Member]
Quantitative information about Level 3 fair value measurements
Servicing Asset, Measurement Input	15.0	58.8
Measurement Input, Discount Rate | Mortgage Servicing Rights [Member] | Level 3 | Weighted Average [Member]
Quantitative information about Level 3 fair value measurements
Servicing Asset, Measurement Input	11.0	10.1
Measurement Input, Constant Prepayment Rate | Mortgage Servicing Rights [Member] | Level 3 | Minimum [Member]
Quantitative information about Level 3 fair value measurements
Servicing Asset, Measurement Input	0.0	0.0
Measurement Input, Constant Prepayment Rate | Mortgage Servicing Rights [Member] | Level 3 | Maximum [Member]
Quantitative information about Level 3 fair value measurements
Servicing Asset, Measurement Input	42.8	69.0
Measurement Input, Constant Prepayment Rate | Mortgage Servicing Rights [Member] | Level 3 | Weighted Average [Member]
Quantitative information about Level 3 fair value measurements
Servicing Asset, Measurement Input	15.4	14.1
Recurring
Quantitative information about Level 3 fair value measurements
Securities available-for-sale, at fair value		$ 8,337