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Basis of Accounting and Consolidation - Additional Information (Details) - USD ($) |  |  | 12 Months Ended |
--- | --- | --- | --- | ---
Mar. 20, 2023 | Feb. 14, 2022 | Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2020
Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |
Common stock, par value (in dollars per share) |  |  | $ 4 | $ 4 |  |
Assets |  |  | $ 7,586,794,000 | $ 6,744,215,000 |  |
Loans |  |  | 5,506,910,000 | 4,766,781,000 |  |
Deposits |  |  | $ 6,123,659,000 | 5,257,001,000 |  |
Federal funds selling period |  |  | 1 day |  |  |
Intangible assets amortization period |  |  | 15 years |  |  |
Captive maximum gross premiums |  |  | $ 2,650,000 |  |  |
Value of trust accounts |  |  | $ 6,100,000,000 | $ 5,300,000,000 |  |
Stock plans, term |  |  | 10 years |  |  |
Maximum number of shares to be issued in stock incentive plan (in shares) |  |  | 149,983 |  |  |
RSA/RSU, grants in period, gross |  |  | 45,986 | 63,150 | 48,575 |
Employee discount for employee stock purchase plan |  |  | 15.00% |  |  |
Employee stock purchase plan, number of shares authorized |  |  | 600,000 |  |  |
Stock issued during period, shares, employee stock purchase plans |  |  | 38,989 | 23,055 | 11,748 |
Right of use lease assets |  |  | $ 14,306,000 | $ 15,774,000 |  |
Lease liability |  |  | 14,615,000 | 16,035,000 |  |
Cumulative change in accounting principal |  |  | 793,204,000 | 633,155,000 | $ 633,894,000 | $ 568,228,000
Allowance for credit losses on loans |  |  | $ 68,675,000 | $ 59,093,000 | $ 54,655,000 | $ 41,910,000
Employee Stock Purchase Plan |  |  |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |
Shares available for issuance |  |  | 506,272 |  |  |
Minimum |  |  |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |
Certificates of deposit investments original maturities period |  |  | 3 years |  |  |
Maximum |  |  |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |
Certificates of deposit investments original maturities period |  |  | 5 years |  |  |
Delta Bancshare Company |  |  |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |
Percentage of issued and outstanding shares acquired |  | 100.00% |  |  |  |
Common stock, par value (in dollars per share) |  | $ 10.00 |  |  |  |
Share Price |  | $ 4.00 |  |  |  |
Consideration payable in cash |  | $ 15,150,000 |  |  |  |
Consideration payable in shares |  | 2,292,270 |  |  |  |
Blackhawk Bancorp, Inc |  |  |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |
Percentage of issued and outstanding shares acquired | 100.00% |  |  |  |  |
Common stock, par value (in dollars per share) | $ 0.01 |  |  |  |  |
Share Price | $ 4 |  |  |  |  |
Consideration payable in cash | $ 1,928 |  |  |  |  |
Consideration payable in shares | 3,290,222 |  |  |  |  |
Conversion of common stock | 1.15 |  |  |  |  |
Common stock consideration value | $ 93,508,000 |  |  |  |  |

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