| 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 March 31, 2021 and December 31, 2020 (dollars in thousands): 
 | 
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 | 
 | 
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 | 
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  | 
      | 
Fair Value Measurements at March 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  | 
  | 
$  | 
 —  | 
  | 
$  | 
 11,677  | 
  | 
$  | 
 —  | 
  | 
$  | 
 11,677  | 
 
Obligations of states and political subdivisions  | 
  | 
   | 
 —  | 
  | 
   | 
 899,098  | 
  | 
   | 
 —  | 
  | 
   | 
 899,098  | 
 
Corporate and other bonds(1)  | 
  | 
   | 
 —  | 
  | 
   | 
 147,608  | 
  | 
   | 
 —  | 
  | 
   | 
 147,608  | 
 
Mortgage-backed securities  | 
  | 
   | 
 —  | 
  | 
   | 
 1,637,035  | 
  | 
   | 
 —  | 
  | 
   | 
 1,637,035  | 
 
Other securities  | 
  | 
   | 
 —  | 
  | 
   | 
 1,625  | 
  | 
   | 
 —  | 
  | 
   | 
 1,625  | 
 
Loans held for sale  | 
  | 
   | 
 —  | 
  | 
   | 
 49,082  | 
  | 
   | 
 —  | 
  | 
   | 
 49,082  | 
 
Derivatives:  | 
  | 
   | 
    | 
  | 
   | 
    | 
  | 
   | 
    | 
  | 
   | 
    | 
 
Interest rate swap  | 
  | 
   | 
 —  | 
  | 
   | 
 106,450  | 
  | 
   | 
 —  | 
  | 
   | 
 106,450  | 
 
Fair value hedges  | 
  | 
   | 
 —  | 
  | 
   | 
 2,139  | 
  | 
   | 
 —  | 
  | 
   | 
 2,139  | 
 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
 
LIABILITIES  | 
  | 
   | 
    | 
  | 
   | 
    | 
  | 
   | 
    | 
  | 
   | 
    | 
 
Derivatives:  | 
  | 
   | 
    | 
  | 
   | 
    | 
  | 
   | 
    | 
  | 
   | 
    | 
 
Interest rate swap  | 
  | 
$  | 
 —  | 
  | 
$  | 
 106,450  | 
  | 
$  | 
 —  | 
  | 
$  | 
 106,450  | 
 
Cash flow hedges  | 
  | 
   | 
 —  | 
  | 
   | 
 1,808  | 
  | 
   | 
 —  | 
  | 
   | 
 1,808  | 
 
Fair value hedges  | 
  | 
   | 
 —  | 
  | 
   | 
 7,949  | 
  | 
   | 
 —  | 
  | 
   | 
 7,949  | 
 
 
| (1) | 
Other bonds include asset-backed securities. | 
  
 
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  | 
      | 
Fair Value Measurements at December 31, 2020 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  | 
  | 
$  | 
 —  | 
  | 
$  | 
 13,394  | 
  | 
$  | 
 —  | 
  | 
$  | 
 13,394  | 
 
Obligations of states and political subdivisions  | 
  | 
  | 
 —  | 
  | 
  | 
 837,326  | 
  | 
  | 
 —  | 
  | 
  | 
 837,326  | 
 
Corporate and other bonds(1)  | 
  | 
   | 
 —  | 
  | 
   | 
 151,078  | 
  | 
   | 
 —  | 
  | 
   | 
 151,078  | 
 
Mortgage-backed securities  | 
  | 
   | 
 —  | 
  | 
   | 
 1,536,996  | 
  | 
   | 
 —  | 
  | 
   | 
 1,536,996  | 
 
Other securities  | 
  | 
   | 
 —  | 
  | 
   | 
 1,625  | 
  | 
   | 
 —  | 
  | 
   | 
 1,625  | 
 
Loans held for sale  | 
  | 
  | 
 —  | 
  | 
  | 
 96,742  | 
  | 
  | 
 —  | 
  | 
  | 
 96,742  | 
 
Derivatives:  | 
  | 
   | 
    | 
  | 
   | 
    | 
  | 
   | 
    | 
  | 
   | 
    | 
 
Interest rate swap  | 
  | 
   | 
 —  | 
  | 
   | 
 163,360  | 
  | 
   | 
 —  | 
  | 
   | 
 163,360  | 
 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
 
LIABILITIES  | 
  | 
   | 
    | 
  | 
   | 
    | 
  | 
   | 
    | 
  | 
   | 
    | 
 
Derivatives:  | 
  | 
   | 
    | 
  | 
   | 
    | 
  | 
   | 
    | 
  | 
   | 
    | 
 
Interest rate swap  | 
  | 
$  | 
 —  | 
  | 
$  | 
 163,360  | 
  | 
$  | 
 —  | 
  | 
$  | 
 163,360  | 
 
Fair value hedges  | 
  | 
   | 
 —  | 
  | 
   | 
 12,483  | 
  | 
   | 
 —  | 
  | 
   | 
 12,483  | 
 
 
| (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 March 31, 2021 and December 31, 2020 are as follows (dollars in thousands): 
 | 
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 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 
  | 
  | 
Fair Value Measurements at March 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  | 
  | 
$  | 
 400,880  | 
  | 
$  | 
 400,880  | 
  | 
$  | 
 —  | 
  | 
$  | 
 —  | 
  | 
$  | 
 400,880  | 
 
AFS securities  | 
  | 
   | 
 2,697,043  | 
  | 
   | 
 —  | 
  | 
   | 
 2,697,043  | 
  | 
   | 
 —  | 
  | 
   | 
 2,697,043  | 
 
HTM securities  | 
  | 
   | 
 543,575  | 
  | 
   | 
 —  | 
  | 
   | 
 593,589  | 
  | 
   | 
 12,770  | 
  | 
   | 
 606,359  | 
 
Restricted stock  | 
  | 
   | 
 76,824  | 
  | 
   | 
 —  | 
  | 
   | 
 76,824  | 
  | 
   | 
 —  | 
  | 
   | 
 76,824  | 
 
Loans held for sale  | 
  | 
   | 
 49,082  | 
  | 
   | 
 —  | 
  | 
   | 
 49,082  | 
  | 
   | 
 —  | 
  | 
   | 
 49,082  | 
 
Net loans  | 
  | 
   | 
 14,129,369  | 
  | 
   | 
 —  | 
  | 
   | 
 —  | 
  | 
   | 
 13,950,754  | 
  | 
   | 
 13,950,754  | 
 
Derivatives:  | 
  | 
   | 
    | 
  | 
   | 
    | 
  | 
   | 
    | 
  | 
   | 
    | 
  | 
   | 
    | 
 
Interest rate swap  | 
  | 
   | 
 106,450  | 
  | 
   | 
 —  | 
  | 
   | 
 106,450  | 
  | 
   | 
 —  | 
  | 
   | 
 106,450  | 
 
Fair value hedges  | 
  | 
   | 
 2,139  | 
  | 
   | 
 —  | 
  | 
   | 
 2,139  | 
  | 
   | 
 —  | 
  | 
   | 
 2,139  | 
 
Accrued interest receivable  | 
  | 
   | 
 74,603  | 
  | 
   | 
 —  | 
  | 
   | 
 74,603  | 
  | 
   | 
 —  | 
  | 
   | 
 74,603  | 
 
BOLI  | 
  | 
   | 
 328,627  | 
  | 
   | 
 —  | 
  | 
   | 
 328,627  | 
  | 
   | 
 —  | 
  | 
   | 
 328,627  | 
 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
 
LIABILITIES  | 
  | 
   | 
    | 
  | 
   | 
    | 
  | 
   | 
    | 
  | 
   | 
    | 
  | 
   | 
    | 
 
Deposits  | 
  | 
$  | 
 16,298,017  | 
  | 
$  | 
 —  | 
  | 
$  | 
 16,328,962  | 
  | 
$  | 
 —  | 
  | 
$  | 
 16,328,962  | 
 
Borrowings  | 
  | 
   | 
 563,600  | 
  | 
   | 
 —  | 
  | 
   | 
 538,488  | 
  | 
   | 
 —  | 
  | 
   | 
 538,488  | 
 
Accrued interest payable  | 
  | 
   | 
 3,561  | 
  | 
   | 
 —  | 
  | 
   | 
 3,561  | 
  | 
   | 
 —  | 
  | 
   | 
 3,561  | 
 
Derivatives:  | 
  | 
   | 
    | 
  | 
   | 
    | 
  | 
   | 
    | 
  | 
   | 
    | 
  | 
   | 
    | 
 
Interest rate swap  | 
  | 
   | 
 106,450  | 
  | 
   | 
 —  | 
  | 
   | 
 106,450  | 
  | 
   | 
 —  | 
  | 
   | 
 106,450  | 
 
Cash flow hedges  | 
  | 
   | 
 1,808  | 
  | 
   | 
 —  | 
  | 
   | 
 1,808  | 
  | 
   | 
 —  | 
  | 
   | 
 1,808  | 
 
Fair value hedges  | 
  | 
   | 
 7,949  | 
  | 
   | 
 —  | 
  | 
   | 
 7,949  | 
  | 
   | 
 —  | 
  | 
   | 
 7,949  | 
 
 
 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 
  | 
      | 
Fair Value Measurements at December 31, 2020 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  | 
  | 
$  | 
 493,294  | 
  | 
$  | 
 493,294  | 
  | 
$  | 
 —  | 
  | 
$  | 
 —  | 
  | 
$  | 
 493,294  | 
 
AFS securities  | 
  | 
   | 
 2,540,419  | 
  | 
   | 
 —  | 
  | 
   | 
 2,540,419  | 
  | 
   | 
 —  | 
  | 
   | 
 2,540,419  | 
 
HTM securities  | 
  | 
   | 
 544,851  | 
  | 
   | 
 —  | 
  | 
   | 
 606,496  | 
  | 
   | 
 13,269  | 
  | 
   | 
 619,765  | 
 
Restricted stock  | 
  | 
   | 
 94,782  | 
  | 
   | 
 —  | 
  | 
   | 
 94,782  | 
  | 
   | 
 —  | 
  | 
   | 
 94,782  | 
 
Loans held for sale  | 
  | 
  | 
 96,742  | 
  | 
  | 
 —  | 
  | 
   | 
 96,742  | 
  | 
   | 
 —  | 
  | 
  | 
 96,742  | 
 
Net loans  | 
  | 
   | 
 13,860,774  | 
  | 
   | 
 —  | 
  | 
   | 
 —  | 
  | 
   | 
 13,710,640  | 
  | 
   | 
 13,710,640  | 
 
Derivatives:  | 
  | 
   | 
    | 
  | 
   | 
    | 
  | 
   | 
    | 
  | 
   | 
    | 
  | 
   | 
    | 
 
Interest rate swap  | 
  | 
   | 
 163,360  | 
  | 
   | 
 —  | 
  | 
   | 
 163,360  | 
  | 
   | 
 —  | 
  | 
   | 
 163,360  | 
 
Accrued interest receivable  | 
  | 
   | 
 75,757  | 
  | 
   | 
 —  | 
  | 
   | 
 75,757  | 
  | 
   | 
 —  | 
  | 
   | 
 75,757  | 
 
BOLI  | 
  | 
   | 
 326,892  | 
  | 
   | 
 —  | 
  | 
   | 
 326,892  | 
  | 
   | 
 —  | 
  | 
   | 
 326,892  | 
 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
 
LIABILITIES  | 
  | 
   | 
    | 
  | 
   | 
    | 
  | 
   | 
    | 
  | 
   | 
    | 
  | 
   | 
    | 
 
Deposits  | 
  | 
$  | 
 15,722,765  | 
  | 
$  | 
 —  | 
  | 
$  | 
 15,763,991  | 
  | 
$  | 
 —  | 
  | 
$  | 
 15,763,991  | 
 
Borrowings  | 
  | 
   | 
 840,717  | 
  | 
   | 
 —  | 
  | 
   | 
 821,516  | 
  | 
   | 
 —  | 
  | 
   | 
 821,516  | 
 
Accrued interest payable  | 
  | 
   | 
 2,516  | 
  | 
   | 
 —  | 
  | 
   | 
 2,516  | 
  | 
   | 
 —  | 
  | 
   | 
 2,516  | 
 
Derivatives:  | 
  | 
   | 
    | 
  | 
   | 
    | 
  | 
   | 
    | 
  | 
   | 
    | 
  | 
   | 
    | 
 
   Interest rate swap  | 
  | 
   | 
 163,360  | 
  | 
   | 
 —  | 
  | 
   | 
 163,360  | 
  | 
   | 
 —  | 
  | 
   | 
 163,360  | 
 
Fair value hedges  | 
  | 
   | 
 12,483  | 
  | 
   | 
 —  | 
  | 
   | 
 12,483  | 
  | 
   | 
 —  | 
  | 
   | 
 12,483  | 
 
 
 |