Fair Values of Financial Instruments - Assets Measured at Fair Value on a Non Recurring Basis and Fair Value of Financial Instruments (Details) $ in Thousands	Sep. 30, 2021 USD ($)	Dec. 31, 2020 USD ($)
Financial Assets
Interest-bearing time deposits with other banks	$ 805	$ 7,021
Nonrecurring | Impaired loans, Residential real estate
Fair value of financial assets and liabilities
Assets measured at fair value on a non-recurring basis	43
Nonrecurring | Impaired loans, Residential real estate | Level 3
Fair value of financial assets and liabilities
Assets measured at fair value on a non-recurring basis	43
Nonrecurring | Impaired loans, Residential real estate | Level 3 | Sales comparison approach
Fair value of financial assets and liabilities
Assets measured at fair value on a non-recurring basis	$ 43
Nonrecurring | Impaired loans, Residential real estate | Weighted Average | Level 3 | Sales comparison approach | Adjustments for differences between the comparable sales
Fair value of financial assets and liabilities
Assets measured at fair value, measurement input	0.15
Nonrecurring | Impaired loans, Commercial real estate
Fair value of financial assets and liabilities
Assets measured at fair value on a non-recurring basis		8,240
Nonrecurring | Impaired loans, Commercial real estate | Level 3
Fair value of financial assets and liabilities
Assets measured at fair value on a non-recurring basis		8,240
Nonrecurring | Impaired loans, Commercial real estate | Level 3 | Sales comparison approach/Income capitalization approach
Fair value of financial assets and liabilities
Assets measured at fair value on a non-recurring basis		$ 8,240
Nonrecurring | Impaired loans, Commercial real estate | Weighted Average | Level 3 | Sales comparison approach/Income capitalization approach | Adjustments for differences between the comparable sales and income data for similar loans and collateral underlying such loans
Fair value of financial assets and liabilities
Assets measured at fair value, measurement input		0.36
Nonrecurring | Impaired loans, Construction
Fair value of financial assets and liabilities
Assets measured at fair value on a non-recurring basis		$ 5,015
Nonrecurring | Impaired loans, Construction | Level 3
Fair value of financial assets and liabilities
Assets measured at fair value on a non-recurring basis		5,015
Nonrecurring | Impaired loans, Construction | Level 3 | Hybrid of sales comparison and income capitalization approaches
Fair value of financial assets and liabilities
Assets measured at fair value on a non-recurring basis		$ 5,015
Nonrecurring | Impaired loans, Construction | Weighted Average | Level 3 | Hybrid of sales comparison and income capitalization approaches | Adjustments for differences between the comparable sales and income data for similar loans and collateral underlying such loans
Fair value of financial assets and liabilities
Assets measured at fair value, measurement input		0.15
Nonrecurring | Mortgage loans held for sale
Fair value of financial assets and liabilities
Assets measured at fair value on a non-recurring basis		$ 19,375
Nonrecurring | Mortgage loans held for sale | Level 2
Fair value of financial assets and liabilities
Assets measured at fair value on a non-recurring basis		19,375
Nonrecurring | Mortgage servicing rights
Fair value of financial assets and liabilities
Assets measured at fair value on a non-recurring basis	$ 2,021	5,175
Nonrecurring | Mortgage servicing rights | Level 3
Fair value of financial assets and liabilities
Assets measured at fair value on a non-recurring basis	2,021	5,175
Nonrecurring | Mortgage servicing rights | Level 3 | Discounted cash flow
Fair value of financial assets and liabilities
Assets measured at fair value on a non-recurring basis	$ 2,021	$ 5,175
Nonrecurring | Mortgage servicing rights | Maximum | Level 3 | Discounted cash flow | Discount rate
Fair value of financial assets and liabilities
Assets measured at fair value, measurement input	0.120	0.120
Nonrecurring | Mortgage servicing rights | Maximum | Level 3 | Discounted cash flow | Prepayment speed
Fair value of financial assets and liabilities
Assets measured at fair value, measurement input	0.377	0.370
Nonrecurring | Mortgage servicing rights | Maximum | Level 3 | Discounted cash flow | Default rate
Fair value of financial assets and liabilities
Assets measured at fair value, measurement input	0.026	0.002
Nonrecurring | Mortgage servicing rights | Minimum | Level 3 | Discounted cash flow | Discount rate
Fair value of financial assets and liabilities
Assets measured at fair value, measurement input	0.095	0.095
Nonrecurring | Mortgage servicing rights | Minimum | Level 3 | Discounted cash flow | Prepayment speed
Fair value of financial assets and liabilities
Assets measured at fair value, measurement input	0.111	0.105
Nonrecurring | Mortgage servicing rights | Minimum | Level 3 | Discounted cash flow | Default rate
Fair value of financial assets and liabilities
Assets measured at fair value, measurement input	0.001	0.001
Nonrecurring | Mortgage servicing rights | Weighted Average | Level 3 | Discounted cash flow | Discount rate
Fair value of financial assets and liabilities
Assets measured at fair value, measurement input	(0.113)	0.116
Nonrecurring | Mortgage servicing rights | Weighted Average | Level 3 | Discounted cash flow | Prepayment speed
Fair value of financial assets and liabilities
Assets measured at fair value, measurement input	(0.212)	0.237
Nonrecurring | Mortgage servicing rights | Weighted Average | Level 3 | Discounted cash flow | Default rate
Fair value of financial assets and liabilities
Assets measured at fair value, measurement input	(0.003)	0.002
Carrying value per balance sheet
Financial Assets
Cash and due from banks	$ 609,412	$ 998,497
Interest-bearing time deposits with other banks	805	7,021
Mortgage loans held for sale	12,744	2,909
Loans, net	2,168,501	2,434,356
Financial Liabilities
Federal Home Loan Bank borrowings	307,000	318,000
Subordinated notes, net	65,360	65,341
Time deposits	961,691	1,646,523
Estimated fair value
Financial Assets
Cash and due from banks	609,412	998,497
Interest-bearing time deposits with other banks	805	7,021
Mortgage loans held for sale	13,266	3,052
Loans, net	2,288,221	2,521,874
Financial Liabilities
Federal Home Loan Bank borrowings	309,868	328,150
Subordinated notes, net	65,066	65,753
Time deposits	964,943	1,658,020
Estimated fair value | Level 1
Financial Assets
Cash and due from banks	609,412	998,497
Interest-bearing time deposits with other banks		7,021
Estimated fair value | Level 2
Financial Assets
Interest-bearing time deposits with other banks	805
Mortgage loans held for sale	13,266	3,052
Financial Liabilities
Federal Home Loan Bank borrowings	309,868	328,150
Subordinated notes, net	65,066	65,753
Time deposits	964,943	1,658,020
Estimated fair value | Level 3
Financial Assets
Loans, net	$ 2,288,221	$ 2,521,874