Fair Value Measurement of Assets and Liabilities - Carrying Amounts and Estimated Fair Values (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest bearing deposits with banks	$ 306,885	$ 1,844,764
Equity securities	35,992	36,473
Total held to maturity debt securities	2,913,851	2,660,605
Accrued interest receivable	102,667	96,882
Deposits with stated maturities	3,414,368	3,687,044
U.S. Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total held to maturity debt securities	68,932	71,661
U.S. government agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total held to maturity debt securities	5,453	6,378
Obligations of states and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total held to maturity debt securities	318,021	344,164
Residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total held to maturity debt securities	2,440,498	2,152,301
Trust preferred securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total held to maturity debt securities	31,733	31,916
Corporate and other debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total held to maturity debt securities	49,214	54,185
Carrying Amount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total held to maturity debt securities	3,073,205	2,668,697
Carrying Amount | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and due from banks	424,035	205,156
Interest bearing deposits with banks	306,885	1,844,764
Accrued interest receivable	102,667	96,882
Deposits without stated maturities	32,232,968	31,945,368
Short-term borrowings	484,181	655,726
Accrued interest payable	8,016	4,909
Carrying Amount | Level 1 | U.S. Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total held to maturity debt securities	67,401	67,558
Carrying Amount | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Federal Reserve Bank and Federal Home Loan Bank stock	195,536	206,450
Deposits with stated maturities	3,414,368	3,687,044
Long-term borrowings	1,409,142	1,423,676
Junior subordinated debentures issued to capital trusts	56,500	56,413
Carrying Amount | Level 2 | U.S. government agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total held to maturity debt securities	5,572	6,265
Carrying Amount | Level 2 | Obligations of states and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total held to maturity debt securities	319,160	337,962
Carrying Amount | Level 2 | Residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total held to maturity debt securities	2,594,295	2,166,142
Carrying Amount | Level 2 | Trust preferred securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total held to maturity debt securities	37,027	37,020
Carrying Amount | Level 2 | Corporate and other debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total held to maturity debt securities	49,750	53,750
Carrying Amount | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	5,464	3,629
Net loans	35,001,895	33,794,455
Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total held to maturity debt securities	2,913,851	2,660,605
Fair Value | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and due from banks	424,035	205,156
Interest bearing deposits with banks	306,885	1,844,764
Accrued interest receivable	102,667	96,882
Deposits without stated maturities	32,232,968	31,945,368
Short-term borrowings	478,300	637,490
Accrued interest payable	8,016	4,909
Fair Value | Level 1 | U.S. Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total held to maturity debt securities	68,932	71,661
Fair Value | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Federal Reserve Bank and Federal Home Loan Bank stock	195,536	206,450
Deposits with stated maturities	3,365,608	3,670,113
Long-term borrowings	1,336,303	1,404,184
Junior subordinated debentures issued to capital trusts	39,578	46,306
Fair Value | Level 2 | U.S. government agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total held to maturity debt securities	5,453	6,378
Fair Value | Level 2 | Obligations of states and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total held to maturity debt securities	318,021	344,164
Fair Value | Level 2 | Residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total held to maturity debt securities	2,440,498	2,152,301
Fair Value | Level 2 | Trust preferred securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total held to maturity debt securities	31,733	31,916
Fair Value | Level 2 | Corporate and other debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total held to maturity debt securities	49,214	54,185
Fair Value | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	5,464	3,629
Net loans	$ 33,815,930	$ 33,283,251