Summary of Significant Accounting Policies (Policies)	3 Months Ended
Mar. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation The accompanying interim condensed consolidated financial statements are prepared in accordance with GAAP for interim financial information and pursuant to the requirements for reporting on Form 10-Q and Article 10 of Regulation S-X of the Securities Exchange Act of 1934. Accordingly, certain disclosures accompanying annual consolidated financial statements are omitted. In the opinion of management, all significant intercompany accounts and transactions have been eliminated and adjustments, consisting solely of normal recurring accruals and considered necessary for the fair presentation of financial statements for the interim periods, have been included. The current period's results of operations are not necessarily indicative of the results that ultimately may be achieved for the year. The interim condensed consolidated financial statements and notes thereto should be read in conjunction with the audited consolidated financial statements and notes thereto included in our Form 10-K for the year ended December 31, 2020, filed with the SEC on March 11, 2021.
Risks and Uncertainties	Risks and Uncertainties The outbreak of COVID-19 has adversely impacted a broad range of industries in which the Company’s customers operate and could impair their ability to fulfill their financial obligations to the Company. The World Health Organization declared COVID-19 to be a global pandemic, indicating that almost all public commerce and related business activities must be, to varying degrees, curtailed with the goal of decreasing the rate of new infections. The spread of the outbreak has caused significant disruptions in the U.S. economy and has disrupted banking and other financial activity in the areas in which the Company operates. While there has been no material impact to the Company’s employees to date, COVID-19 could also potentially create widespread business continuity issues for the Company. Congress, the President, and the FRB have taken several actions designed to mitigate the economic impact of the pandemic. The CARES Act was signed into law in March 2020 as a $2 trillion legislative package. In addition to the general impact of COVID-19, certain provisions of the CARES Act as well as other recent legislative and regulatory relief efforts are expected to have a material impact on the Company’s operations. On December 27, 2020, a new COVID-19 relief bill was signed into law by President Trump, which includes as part of the bill up to $284.5 billion of a second wave of PPP funding. The American Rescue Plan Act of 2021 was signed into law on March 11, 2021 by President Biden as a $1.9 trillion legislative package, which includes as part of the bill a variety of economic assistance programs for Americans. In addition, on March 30, 2021, President Biden signed into law the PPP Extension Act of 2021, which provided an extension to May 31, 2021 for qualifying businesses to apply for a PPP loan and provided an additional 30 days for the SBA to process pending PPP loan applications. The Company’s business is dependent upon the willingness and ability of its employees and customers to conduct banking and other financial transactions. If the global response to contain COVID-19 escalates further or is unsuccessful, the Company could experience a material adverse effect on its business, financial condition, results of operations and cash flows. While it is not possible to know the full universe or extent that the impact of COVID-19, and related measures to curtail its spread or to provide economic assistance to entities and individuals or otherwise stimulate the economy, will have on the Company’s operations, the Company discloses in this report potentially material items of which it is aware at the time this report is filed with the SEC. Financial position and results of operations The Company’s interest income could be reduced due to COVID-19. In accordance with CARES Act provisions and regulatory guidance, the Company is actively working with COVID-19 affected borrowers to defer their payments, interest, and fees. While interest and fees will still accrue to income, through normal GAAP accounting, should eventual credit losses on these deferred payments emerge, interest income and fees accrued would need to be reversed. In such a scenario, interest income in future periods could be negatively impacted. At this time, the Company is unable to project the materiality of such an impact, but recognizes that the breadth of the economic impact of COVID-19 may affect its borrowers’ ability to repay in future periods. Capital and liquidity While the Company believes that it has sufficient capital to withstand an extended economic recession brought about by COVID-19, its reported and regulatory capital ratios could be adversely impacted by further credit losses. The Company relies on cash on hand as well as dividends from its subsidiary bank to service its debt. If the Company’s capital deteriorates such that its subsidiary bank is unable to pay dividends to it for an extended period of time, the Company may not be able to service its debt. If an extended recession causes large numbers of the Company’s deposit customers to withdraw their funds, the Company might become more reliant on volatile or more expensive sources of funding. Asset valuation Currently, the Company does not expect COVID-19 to affect its ability to account timely for the assets on its balance sheet; however, this could change in future periods. While certain valuation assumptions and judgments will change to account for pandemic-related circumstances such as widening credit spreads, the Company does not anticipate significant changes in methodology used to determine the fair value of assets measured in accordance with GAAP. It is possible that the lingering effects of COVID-19 could cause the occurrence of what management would deem to be subsequent triggering events that could, under certain circumstances, cause us to perform a goodwill or intangible asset impairment test and result in an impairment charge being recorded for that period. In the event that the Company concludes that all or a portion of its goodwill or intangible assets is impaired, a non-cash charge for the amount of such impairment would be recorded to earnings. Such a charge would have no impact on tangible capital or regulatory capital, cash flows or liquidity position. Credit The Company is working with customers directly affected by COVID-19. The Company has offered and continues to offer short-term assistance in accordance with regulatory guidelines. As a result of the current economic environment caused by the COVID-19 pandemic, the Company is engaging in more frequent communication with borrowers to better understand their situations and the challenges faced, allowing it to respond proactively as needs and issues arise. Should economic conditions worsen, the Company could experience further increases in its required ACL and record additional credit loss expense. It is possible that the Company’s asset quality measures could worsen in future periods if the effects of COVID-19 are prolonged.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect: (1) the reported amounts of assets and liabilities, (2) the disclosure of contingent assets and liabilities at the date of the financial statements, and (3) the reported amounts of revenues and expenses during the reporting period. These estimates are based on information available to management at the time the estimates are made. Actual results could differ from those estimates. The results for the three months ended March 31, 2021 may not be indicative of results for the year ending December 31, 2021, or for any other period. All significant accounting policies followed in the preparation of the quarterly financial statements are disclosed in the Annual Report on Form 10-K for the year ended December 31, 2020, filed with the SEC on March 11, 2021.
Segment Reporting	Segment Reporting The Company’s activities are considered to be one reportable segment. The Company is engaged in the business of commercial and retail banking, and trust and investment services, with operations throughout Iowa, the Minneapolis/St. Paul metropolitan area of Minnesota, western Wisconsin, Naples and Fort Myers, Florida, and Denver, Colorado. Substantially all income is derived from a diverse base of commercial, mortgage and retail lending activities, and investments.
Effect of New Financial Accounting Standards	Effect of New Financial Accounting StandardsAccounting Guidance Pending Adoption at March 31, 2021On March 12, 2020, the FASB issued ASU 2020-04, Reference Rate Reform (ASC 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting. ASC 848 contains optional expedients and exceptions for applying GAAP to contracts, hedging relationships, and other transactions affected by reference rate reform. Entities may apply the provision as of the beginning of the reporting period when the election is made until December 31, 2022. The Company is currently evaluating the impact of ASU 2020-04.
Derivatives	Derivatives Designated as Hedging Instruments The Company uses derivative instruments to hedge its exposure to economic risks, including interest rate, liquidity, and credit risk. Certain hedging relationships are formally designated and qualify for hedge accounting under GAAP as fair value or cash flow hedges. Fair Value Hedges - Derivatives are designated as fair value hedges to limit the Company's exposure to changes in the fair value of assets or liabilities due to movements in interest rates. The Company entered into pay-fixed receive-floating interest rate swaps to manage its exposure to changes in fair value in certain fixed-rate assets. The gain or loss on the derivative as well as the offsetting loss or gain on the hedged item attributable to the hedged risk are recognized in interest income. Cash Flow Hedges - Derivatives are designated as cash flow hedges in order to minimize the variability in cash flows of earning assets or forecasted transactions caused by movement in interest rates. In February 2020, the Company entered into a pay-fixed receive-variable interest rate swap with a notional amount of $30.0 million to hedge against adverse fluctuations in interest rates by reducing exposure to variability in cash flows relating to interest payments on the Company's variable rate debt. The interest rate swap was designated as a cash flow hedge. The gain or loss on the derivative was recorded in accumulated other comprehensive income and subsequently reclassified into interest expense in the same period(s) during which the hedged transaction affects earnings. The Company terminated its cash flow hedge in the fourth quarter of 2020.
Fair Value Measurements	Fair value is the exchange price that would be received for an asset or paid to transfer a liability (exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. There are three levels of inputs that may be used to measure fair values: •Level 1 – Quoted prices (unadjusted) for identical assets or liabilities in active markets that the entity has the ability to access as of the measurement date. •Level 2 – Significant other observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities, quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data. •Level 3 – Significant unobservable inputs that reflect a company’s own assumptions about the assumptions that market participants would use in pricing an asset or liability. For information regarding the valuation methodologies used to measure the Company's assets recorded at fair value (under ASC Topic 820), and for estimating fair value for financial instruments not recorded at fair value (under ASC Topic 825, as amended by ASU 2016-01 and ASU 2018-03), see Note 1. Nature of Business and Significant Accounting Policies and Note 20. Estimated Fair Value of Financial Instruments and Fair Value Measurements to the consolidated financial statements in the Company's 2020 Annual Report on Form 10-K, filed with the SEC on March 11, 2021. The Company uses fair value to measure certain assets and liabilities on a recurring basis, primarily available for sale debt securities, derivatives and mortgage servicing rights. For assets measured at the lower of cost or fair value, the fair value measurement criteria may or may not be met during a reporting period and such measurements are therefore considered "nonrecurring" for purposes of disclosing the Company's fair value measurements. Fair value is used on a nonrecurring basis to adjust carrying values for collateral dependent individually analyzed loans and other real estate owned.

Summary of Significant Accounting Policies (Policies)

3 Months Ended

Mar. 31, 2021

Organization, Consolidation and Presentation of Financial Statements [Abstract]

The accompanying interim condensed consolidated financial statements are prepared in accordance with GAAP for interim financial information and pursuant to the requirements for reporting on Form 10-Q and Article 10 of Regulation S-X of the Securities Exchange Act of 1934. Accordingly, certain disclosures accompanying annual consolidated financial statements are omitted. In the opinion of management, all significant intercompany accounts and transactions have been eliminated and adjustments, consisting solely of normal recurring accruals and considered necessary for the fair presentation of financial statements for the interim periods, have been included. The current period's results of operations are not necessarily indicative of the results that ultimately may be achieved for the year. The interim condensed consolidated financial statements and notes thereto should be read in conjunction with the audited consolidated financial statements and notes thereto included in our Form 10-K for the year ended December 31, 2020, filed with the SEC on March 11, 2021.

Risks and Uncertainties

The outbreak of COVID-19 has adversely impacted a broad range of industries in which the Company’s customers operate and could impair their ability to fulfill their financial obligations to the Company. The World Health Organization declared COVID-19 to be a global pandemic, indicating that almost all public commerce and related business activities must be, to varying degrees, curtailed with the goal of decreasing the rate of new infections. The spread of the outbreak has caused significant disruptions in the U.S. economy and has disrupted banking and other financial activity in the areas in which the Company operates. While there has been no material impact to the Company’s employees to date, COVID-19 could also potentially create widespread business continuity issues for the Company.

Congress, the President, and the FRB have taken several actions designed to mitigate the economic impact of the pandemic. The CARES Act was signed into law in March 2020 as a $2 trillion legislative package. In addition to the general impact of COVID-19, certain provisions of the CARES Act as well as other recent legislative and regulatory relief efforts are expected to have a material impact on the Company’s operations. On December 27, 2020, a new COVID-19 relief bill was signed into law by President Trump, which includes as part of the bill up to $284.5 billion of a second wave of PPP funding. The American Rescue Plan Act of 2021 was signed into law on March 11, 2021 by President Biden as a $1.9 trillion legislative package, which includes as part of the bill a variety of economic assistance programs for Americans. In addition, on March 30, 2021, President Biden signed into law the PPP Extension Act of 2021, which provided an extension to May 31, 2021 for qualifying businesses to apply for a PPP loan and provided an additional 30 days for the SBA to process pending PPP loan applications.

The Company’s business is dependent upon the willingness and ability of its employees and customers to conduct banking and other financial transactions. If the global response to contain COVID-19 escalates further or is unsuccessful, the Company could experience a material adverse effect on its business, financial condition, results of operations and cash flows. While it is not possible to know the full universe or extent that the impact of COVID-19, and related measures to curtail its spread or to provide economic assistance to entities and individuals or otherwise stimulate the economy, will have on the Company’s operations, the Company discloses in this report potentially material items of which it is aware at the time this report is filed with the SEC.

Financial position and results of operations

The Company’s interest income could be reduced due to COVID-19. In accordance with CARES Act provisions and regulatory guidance, the Company is actively working with COVID-19 affected borrowers to defer their payments, interest, and fees. While interest and fees will still accrue to income, through normal GAAP accounting, should eventual credit losses on these deferred payments emerge, interest income and fees accrued would need to be reversed. In such a scenario, interest income in future periods could be negatively impacted. At this time, the Company is unable to project the materiality of such

an impact, but recognizes that the breadth of the economic impact of COVID-19 may affect its borrowers’ ability to repay in future periods.

Capital and liquidity

While the Company believes that it has sufficient capital to withstand an extended economic recession brought about by COVID-19, its reported and regulatory capital ratios could be adversely impacted by further credit losses. The Company relies on cash on hand as well as dividends from its subsidiary bank to service its debt. If the Company’s capital deteriorates such that its subsidiary bank is unable to pay dividends to it for an extended period of time, the Company may not be able to service its debt. If an extended recession causes large numbers of the Company’s deposit customers to withdraw their funds, the Company might become more reliant on volatile or more expensive sources of funding.

Asset valuation

Currently, the Company does not expect COVID-19 to affect its ability to account timely for the assets on its balance sheet; however, this could change in future periods. While certain valuation assumptions and judgments will change to account for pandemic-related circumstances such as widening credit spreads, the Company does not anticipate significant changes in methodology used to determine the fair value of assets measured in accordance with GAAP.

It is possible that the lingering effects of COVID-19 could cause the occurrence of what management would deem to be subsequent triggering events that could, under certain circumstances, cause us to perform a goodwill or intangible asset impairment test and result in an impairment charge being recorded for that period. In the event that the Company concludes that all or a portion of its goodwill or intangible assets is impaired, a non-cash charge for the amount of such impairment would be recorded to earnings. Such a charge would have no impact on tangible capital or regulatory capital, cash flows or liquidity position.

Credit

The Company is working with customers directly affected by COVID-19. The Company has offered and continues to offer short-term assistance in accordance with regulatory guidelines. As a result of the current economic environment caused by the COVID-19 pandemic, the Company is engaging in more frequent communication with borrowers to better understand their situations and the challenges faced, allowing it to respond proactively as needs and issues arise. Should economic conditions worsen, the Company could experience further increases in its required ACL and record additional credit loss expense. It is possible that the Company’s asset quality measures could worsen in future periods if the effects of COVID-19 are prolonged.

Use of Estimates

The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect: (1) the reported amounts of assets and liabilities, (2) the disclosure of contingent assets and liabilities at the date of the financial statements, and (3) the reported amounts of revenues and expenses during the reporting period. These estimates are based on information available to management at the time the estimates are made. Actual results could differ from those estimates. The results for the three months ended March 31, 2021 may not be indicative of results for the year ending December 31, 2021, or for any other period.

All significant accounting policies followed in the preparation of the quarterly financial statements are disclosed in the Annual Report on Form 10-K for the year ended December 31, 2020, filed with the SEC on March 11, 2021.

Segment Reporting

The Company’s activities are considered to be one reportable segment. The Company is engaged in the business of commercial and retail banking, and trust and investment services, with operations throughout Iowa, the Minneapolis/St. Paul metropolitan area of Minnesota, western Wisconsin, Naples and Fort Myers, Florida, and Denver, Colorado. Substantially all income is derived from a diverse base of commercial, mortgage and retail lending activities, and investments.

Effect of New Financial Accounting Standards

Effect of New Financial Accounting StandardsAccounting Guidance Pending Adoption at March 31, 2021On March 12, 2020, the FASB issued ASU 2020-04, Reference Rate Reform (ASC 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting. ASC 848 contains optional expedients and exceptions for applying GAAP to contracts, hedging relationships, and other transactions affected by reference rate reform. Entities may apply the provision as of the beginning of the reporting period when the election is made until December 31, 2022. The Company is currently evaluating the impact of ASU 2020-04.

Derivatives

Derivatives Designated as Hedging Instruments

The Company uses derivative instruments to hedge its exposure to economic risks, including interest rate, liquidity, and credit risk. Certain hedging relationships are formally designated and qualify for hedge accounting under GAAP as fair value or cash flow hedges.

Fair Value Hedges - Derivatives are designated as fair value hedges to limit the Company's exposure to changes in the fair value of assets or liabilities due to movements in interest rates. The Company entered into pay-fixed receive-floating interest rate swaps to manage its exposure to changes in fair value in certain fixed-rate assets. The gain or loss on the derivative as well as the offsetting loss or gain on the hedged item attributable to the hedged risk are recognized in interest income.

Cash Flow Hedges - Derivatives are designated as cash flow hedges in order to minimize the variability in cash flows of earning assets or forecasted transactions caused by movement in interest rates. In February 2020, the Company entered into a pay-fixed receive-variable interest rate swap with a notional amount of $30.0 million to hedge against adverse fluctuations in interest rates by reducing exposure to variability in cash flows relating to interest payments on the Company's variable rate debt. The interest rate swap was designated as a cash flow hedge. The gain or loss on the derivative was recorded in accumulated other comprehensive income and subsequently reclassified into interest expense in the same period(s) during which the hedged transaction affects earnings. The Company terminated its cash flow hedge in the fourth quarter of 2020.

Fair Value Measurements

Fair value is the exchange price that would be received for an asset or paid to transfer a liability (exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. There are three levels of inputs that may be used to measure fair values:

•Level 1 – Quoted prices (unadjusted) for identical assets or liabilities in active markets that the entity has the ability to access as of the measurement date.

•Level 2 – Significant other observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities, quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data.

•Level 3 – Significant unobservable inputs that reflect a company’s own assumptions about the assumptions that market participants would use in pricing an asset or liability.

For information regarding the valuation methodologies used to measure the Company's assets recorded at fair value (under ASC Topic 820), and for estimating fair value for financial instruments not recorded at fair value (under ASC Topic 825, as amended by ASU 2016-01 and ASU 2018-03), see Note 1. Nature of Business and Significant Accounting Policies and Note 20. Estimated Fair Value of Financial Instruments and Fair Value Measurements to the consolidated financial statements in the Company's 2020 Annual Report on Form 10-K, filed with the SEC on March 11, 2021.

The Company uses fair value to measure certain assets and liabilities on a recurring basis, primarily available for sale debt securities, derivatives and mortgage servicing rights. For assets measured at the lower of cost or fair value, the fair value measurement criteria may or may not be met during a reporting period and such measurements are therefore considered "nonrecurring" for purposes of disclosing the Company's fair value measurements. Fair value is used on a nonrecurring basis to adjust carrying values for collateral dependent individually analyzed loans and other real estate owned.