Fair Value Measurement of Assets and Liabilities - Carrying Amounts and Estimated Fair Values (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Assets
Interest bearing deposits with banks	$ 1,491,091	$ 503,622
Equity securities	61,010	48,731
Total held to maturity debt securities	3,278,948	3,329,470
Accrued interest receivable	225,918	196,606
Liabilities
Deposits with stated maturities	14,908,182	9,556,457
U.S. Treasury securities
Assets
Total held to maturity debt securities	65,675	65,889
U.S. government agency securities
Assets
Total held to maturity debt securities	215,039	212,712
Obligations of states and political subdivisions
Assets
Total held to maturity debt securities	438,991	453,195
Residential mortgage-backed securities
Assets
Total held to maturity debt securities	2,461,519	2,495,797
Trust preferred securities
Assets
Total held to maturity debt securities	29,344	31,106
Corporate and other debt securities
Assets
Total held to maturity debt securities	68,380	70,771
Carrying Amount
Assets
Total held to maturity debt securities	3,766,838	3,828,984
Carrying Amount | Level 1
Assets
Cash and due from banks	463,318	444,325
Interest bearing deposits with banks	1,491,091	503,622
Accrued interest receivable	225,918	196,606
Liabilities
Deposits without stated maturities	34,711,633	38,080,457
Short-term borrowings	1,088,899	138,729
Accrued interest payable	125,873	45,617
Carrying Amount | Level 1 | U.S. Treasury securities
Assets
Total held to maturity debt securities	66,579	66,911
Carrying Amount | Level 2
Assets
Federal reserve bank and federal home loan bank stock	326,959	238,056
Liabilities
Deposits with stated maturities	14,908,182	9,556,457
Long-term borrowings	2,443,533	1,543,058
Junior subordinated debentures issued to capital trusts	56,934	56,760
Carrying Amount | Level 2 | U.S. government agency securities
Assets
Total held to maturity debt securities	261,197	260,392
Carrying Amount | Level 2 | Obligations of states and political subdivisions
Assets
Total held to maturity debt securities	465,115	480,298
Carrying Amount | Level 2 | Residential mortgage-backed securities
Assets
Total held to maturity debt securities	2,861,227	2,909,106
Carrying Amount | Level 2 | Trust preferred securities
Assets
Total held to maturity debt securities	37,052	37,043
Carrying Amount | Level 2 | Corporate and other debt securities
Assets
Total held to maturity debt securities	75,668	75,234
Carrying Amount | Level 3
Assets
Equity securities	25,047	15,138
Net loans	49,440,816	46,458,545
Fair Value
Assets
Total held to maturity debt securities	3,278,948	3,329,470
Fair Value | Level 1
Assets
Cash and due from banks	463,318	444,325
Interest bearing deposits with banks	1,491,091	503,622
Accrued interest receivable	225,918	196,606
Liabilities
Deposits without stated maturities	34,711,633	38,080,457
Short-term borrowings	1,066,450	138,729
Accrued interest payable	125,873	45,617
Fair Value | Level 1 | U.S. Treasury securities
Assets
Total held to maturity debt securities	65,675	65,889
Fair Value | Level 2
Assets
Federal reserve bank and federal home loan bank stock	326,959	238,056
Liabilities
Deposits with stated maturities	14,783,271	9,443,253
Long-term borrowings	2,340,324	1,395,991
Junior subordinated debentures issued to capital trusts	48,117	50,923
Fair Value | Level 2 | U.S. government agency securities
Assets
Total held to maturity debt securities	215,039	212,712
Fair Value | Level 2 | Obligations of states and political subdivisions
Assets
Total held to maturity debt securities	438,991	453,195
Fair Value | Level 2 | Residential mortgage-backed securities
Assets
Total held to maturity debt securities	2,461,519	2,495,797
Fair Value | Level 2 | Trust preferred securities
Assets
Total held to maturity debt securities	29,344	31,106
Fair Value | Level 2 | Corporate and other debt securities
Assets
Total held to maturity debt securities	68,380	70,771
Fair Value | Level 3
Assets
Equity securities	25,047	15,138
Net loans	$ 47,472,065	$ 44,910,049