| Schedule of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis | The following table presents the balances of financial assets and liabilities measured at fair value on a recurring basis at September 30, 2022 and December 31, 2021 (dollars in thousands): 
|  |  |  |  |  |  |  |  |  |  |  |  |  |  
|  |      | Fair Value Measurements at September 30, 2022 using |  
|  |      |  |  |      | Significant |      |  |  |      |  |  |  
|  |  | Quoted Prices in |  | Other |  | Significant |  |  |  |  
|  |  | Active Markets for |  | Observable |  | Unobservable |  |  |  |  
|  |  | Identical Assets |  | Inputs |  | Inputs |  |  |  |  
|  |  | Level 1 |  | Level 2 |  | Level 3 |  | Balance |  
| ASSETS |  |  |    |   |  |    |   |  |    |   |  |    |  
| AFS securities: |  |  |    |   |  |    |   |  |    |   |  |    |  
| U.S. government and agency securities |  | $ |  56,073 |  | $ |  5,563 |  | $ |  — |  | $ |  61,636 |  
| Obligations of states and political subdivisions |  |   |  — |  |   |  764,543 |  |   |  — |  |   |  764,543 |  
| Corporate and other bonds(1) |  |   |  — |  |   |  231,088 |  |   |  — |  |   |  231,088 |  
| MBS |  |   |  — |  |   |  1,658,402 |  |   |  — |  |   |  1,658,402 |  
| Other securities |  |   |  — |  |   |  1,654 |  |   |  — |  |   |  1,654 |  
| LHFS |  |   |  — |  |   |  12,889 |  |   |  — |  |   |  12,889 |  
| Derivatives: |  |   |    |  |   |    |  |   |    |  |   |    |  
| Interest rate contracts(2) |  |   |  — |  |   |  72,627 |  |   |  — |  |   |  72,627 |  
| Fair value hedges |  |   |  — |  |   |  4,511 |  |   |  — |  |   |  4,511 |  
|  |  |  |  |  |  |  |  |  |  |  |  |  |  
| LIABILITIES |  |  |  |  |  |  |  |  |  |  |  |  |  
| Derivatives: |  |   |    |  |   |    |  |   |    |  |   |    |  
| Interest rate contracts(2) |  | $ |  — |  | $ |  242,969 |  | $ |  — |  | $ |  242,969 |  
| Cash flow hedges |  |   |  — |  |   |  7,735 |  |   |  — |  |   |  7,735 |  
|  |  |  |  |  |  |  |  |  |  |  |  |  |  (1) Other bonds include asset-backed securities. (2) Includes RPAs.   
|  |  |  |  |  |  |  |  |  |  |  |  |  |  
|  |      | Fair Value Measurements at December 31, 2021 using |  
|  |      |  |  |      | Significant |      |  |  |      |  |  |  
|  |  | Quoted Prices in |  | Other |  | Significant |  |  |  |  
|  |  | Active Markets for |  | Observable |  | Unobservable |  |  |  |  
|  |  | Identical Assets |  | Inputs |  | Inputs |  |  |  |  
|  |  | Level 1 |  | Level 2 |  | Level 3 |  | Balance |  
| ASSETS |  |  |    |   |  |    |   |  |    |   |  |    |  
| AFS securities: |  |  |    |   |  |    |   |  |    |   |  |    |  
| U.S. government and agency securities |  | $ |  64,474 |  | $ |  9,375 |  | $ |  — |  | $ |  73,849 |  
| Obligations of states and political subdivisions |  |  |  — |  |  |  1,008,396 |  |  |  — |  |  |  1,008,396 |  
| Corporate and other bonds(1) |  |   |  — |  |   |  153,376 |  |   |  — |  |   |  153,376 |  
| MBS |  |   |  — |  |   |  2,244,389 |  |   |  — |  |   |  2,244,389 |  
| Other securities |  |   |  — |  |   |  1,640 |  |   |  — |  |   |  1,640 |  
| LHFS |  |  |  — |  |  |  20,861 |  |  |  — |  |  |  20,861 |  
| Derivatives: |  |   |    |  |   |    |  |   |    |  |   |    |  
| Interest rate contracts |  |   |  — |  |   |  73,696 |  |   |  — |  |   |  73,696 |  
|  |  |  |  |  |  |  |  |  |  |  |  |  |  
| LIABILITIES |  |   |    |  |   |    |  |   |    |  |   |    |  
| Derivatives: |  |   |    |  |   |    |  |   |    |  |   |    |  
| Interest rate contracts |  | $ |  — |  | $ |  49,051 |  | $ |  — |  | $ |  49,051 |  
| Fair value hedges |  |   |  — |  |   |  5,387 |  |   |  — |  |   |  5,387 |  
|  |  |  |  |  |  |  |  |  |  |  |  |  |  (1) Other bonds include asset-backed securities. | 
| Carrying Values and Estimated Fair Values of the Company's Financial Instruments |  The carrying values and estimated fair values of the Company’s financial instruments at September 30, 2022 and December 31, 2021 are as follows (dollars in thousands): 
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
|  |  | Fair Value Measurements at September 30, 2022 using |  
|  |      |  |  |      | Quoted Prices |      | Significant |      |  |  |      |  |  |  
|  |  |  |  |  | in Active |  | Other |  | Significant |  |  |  |  
|  |  |  |  |  | Markets for |  | Observable |  | Unobservable |  | Total Fair |  
|  |  |  |  |  | Identical Assets |  | Inputs |  | Inputs |  | Value |  
|  |  | Carrying |  |  |  |  |  |  |  |  |  |  |  |  |  
|  |   | Value |  | Level 1 |  | Level 2 |  | Level 3 |  | Balance |  
| ASSETS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
| Cash and cash equivalents |  | $ |  390,942 |  | $ |  390,942 |  | $ |  — |  | $ |  — |  | $ |  390,942 |  
| AFS securities |  |   |  2,717,323 |  |   |  56,073 |  |   |  2,661,250 |  |   |  — |  |   |  2,717,323 |  
| HTM securities |  |   |  841,349 |  |   |  — |  |   |  762,307 |  |   |  3,173 |  |   |  765,480 |  
| Restricted stock |  |   |  82,050 |  |   |  — |  |   |  82,050 |  |   |  — |  |   |  82,050 |  
| LHFS |  |   |  12,889 |  |   |  — |  |   |  12,889 |  |   |  — |  |   |  12,889 |  
| Net loans |  |   |  13,810,711 |  |   |  — |  |   |  — |  |   |  13,330,986 |  |   |  13,330,986 |  
| Derivatives: |  |   |    |  |   |    |  |   |    |  |   |    |  |   |    |  
| Interest rate contracts(1) |  |   |  72,627 |  |   |  — |  |   |  72,627 |  |   |  — |  |   |  72,627 |  
| Fair value hedges |  |   |  4,511 |  |   |  — |  |   |  4,511 |  |   |  — |  |   |  4,511 |  
| Accrued interest receivable |  |   |  68,747 |  |   |  — |  |   |  68,747 |  |   |  — |  |   |  68,747 |  
| BOLI |  |   |  437,988 |  |   |  — |  |   |  437,988 |  |   |  — |  |   |  437,988 |  
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
| LIABILITIES |  |   |    |  |   |    |  |   |    |  |   |    |  |   |    |  
| Deposits |  | $ |  16,546,216 |  | $ |  — |  | $ |  16,560,956 |  | $ |  — |  | $ |  16,560,956 |  
| Borrowings |  |   |  669,558 |  |   |  — |  |   |  605,018 |  |   |  — |  |   |  605,018 |  
| Accrued interest payable |  |   |  3,910 |  |   |  — |  |   |  3,910 |  |   |  — |  |   |  3,910 |  
| Derivatives: |  |   |    |  |   |    |  |   |    |  |   |    |  |   |    |  
| Interest rate contracts(1) |  |   |  242,969 |  |   |  — |  |   |  242,969 |  |   |  — |  |   |  242,969 |  
| Cash flow hedges |  |   |  7,735 |  |   |  — |  |   |  7,735 |  |   |  — |  |   |  7,735 |  
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  (1) Includes RPAs.  
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
|  |      | Fair Value Measurements at December 31, 2021 using |  
|  |  |  |  |  | Quoted Prices |  | Significant |  |  |  |  |  |  |  
|  |  |  |  |  | in Active |  | Other |  | Significant |  |  |  |  
|  |  |  |  |  | Markets for |  | Observable |  | Unobservable |  | Total Fair |  
|  |  |  |  |  | Identical Assets |  | Inputs |  | Inputs |  | Value |  
|  |  | Carrying |  |  |  |  |  |  |  |  |  |  |  |  |  
|  |  | Value |  | Level 1 |  | Level 2 |  | Level 3 |  | Balance |  
| ASSETS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
| Cash and cash equivalents |  | $ |  802,501 |  | $ |  802,501 |  | $ |  — |  | $ |  — |  | $ |  802,501 |  
| AFS securities |  |   |  3,481,650 |  |   |  64,474 |  |   |  3,417,176 |  |   |  — |  |   |  3,481,650 |  
| HTM securities |  |   |  628,000 |  |   |  — |  |   |  686,733 |  |   |  7,041 |  |   |  693,774 |  
| Restricted stock |  |   |  76,825 |  |   |  — |  |   |  76,825 |  |   |  — |  |   |  76,825 |  
| LHFS |  |  |  20,861 |  |  |  — |  |   |  20,861 |  |   |  — |  |  |  20,861 |  
| Net loans |  |   |  13,096,056 |  |   |  — |  |   |  — |  |   |  12,861,274 |  |   |  12,861,274 |  
| Derivatives: |  |   |    |  |   |    |  |   |    |  |   |    |  |   |    |  
| Interest rate contracts |  |   |  73,696 |  |   |  — |  |   |  73,696 |  |   |  — |  |   |  73,696 |  
| Accrued interest receivable |  |   |  65,015 |  |   |  — |  |   |  65,015 |  |   |  — |  |   |  65,015 |  
| BOLI |  |   |  431,517 |  |   |  — |  |   |  431,517 |  |   |  — |  |   |  431,517 |  
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
| LIABILITIES |  |   |    |  |   |    |  |   |    |  |   |    |  |   |    |  
| Deposits |  | $ |  16,611,068 |  | $ |  — |  | $ |  16,630,087 |  | $ |  — |  | $ |  16,630,087 |  
| Borrowings |  |   |  506,594 |  |   |  — |  |   |  488,796 |  |   |  — |  |   |  488,796 |  
| Accrued interest payable |  |   |  933 |  |   |  — |  |   |  933 |  |   |  — |  |   |  933 |  
| Derivatives: |  |   |    |  |   |    |  |   |    |  |   |    |  |   |    |  
|    Interest rate contracts |  |   |  49,051 |  |   |  — |  |   |  49,051 |  |   |  — |  |   |  49,051 |  
| Fair value hedges |  |   |  5,387 |  |   |  — |  |   |  5,387 |  |   |  — |  |   |  5,387 |  |