Fair Value Measurement of Assets and Liabilities - Carrying Amounts and Estimated Fair Values (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Assets
Interest bearing deposits with banks	$ 5,260,998	$ 503,622
Equity securities	50,152	48,731
Total held to maturity debt securities	3,400,484	3,329,470
Accrued interest receivable	223,608	196,606
Liabilities
Deposits with stated maturities	11,111,376	9,556,457
U.S. Treasury securities
Assets
Total held to maturity debt securities	66,182	65,889
U.S. government agency securities
Assets
Total held to maturity debt securities	255,640	212,712
Obligations of states and political subdivisions
Assets
Total held to maturity debt securities	452,919	453,195
Residential mortgage-backed securities
Assets
Total held to maturity debt securities	2,525,568	2,495,797
Trust preferred securities
Assets
Total held to maturity debt securities	29,992	31,106
Corporate and other debt securities
Assets
Total held to maturity debt securities	70,183	70,771
Carrying Amount
Assets
Total held to maturity debt securities	3,847,212	3,828,984
Carrying Amount | Level 1
Assets
Cash and due from banks	444,690	444,325
Interest bearing deposits with banks	5,260,998	503,622
Accrued interest receivable	223,608	196,606
Liabilities
Deposits without stated maturities	36,479,540	38,080,457
Short-term borrowings	6,413,056	138,729
Accrued interest payable	85,581	45,617
Carrying Amount | Level 1 | U.S. Treasury securities
Assets
Total held to maturity debt securities	66,747	66,911
Carrying Amount | Level 2
Assets
Federal reserve bank and federal home loan bank stock	547,686	238,056
Liabilities
Deposits with stated maturities	11,111,376	9,556,457
Long-term borrowings	2,197,656	1,543,058
Junior subordinated debentures issued to capital trusts	56,847	56,760
Carrying Amount | Level 2 | U.S. government agency securities
Assets
Total held to maturity debt securities	300,614	260,392
Carrying Amount | Level 2 | Obligations of states and political subdivisions
Assets
Total held to maturity debt securities	473,597	480,298
Carrying Amount | Level 2 | Residential mortgage-backed securities
Assets
Total held to maturity debt securities	2,893,505	2,909,106
Carrying Amount | Level 2 | Trust preferred securities
Assets
Total held to maturity debt securities	37,048	37,043
Carrying Amount | Level 2 | Corporate and other debt securities
Assets
Total held to maturity debt securities	75,701	75,234
Carrying Amount | Level 3
Assets
Equity securities	16,342	15,138
Net loans	48,223,068	46,458,545
Fair Value
Assets
Total held to maturity debt securities	3,400,484	3,329,470
Fair Value | Level 1
Assets
Cash and due from banks	444,690	444,325
Interest bearing deposits with banks	5,260,998	503,622
Accrued interest receivable	223,608	196,606
Liabilities
Deposits without stated maturities	36,479,540	38,080,457
Short-term borrowings	6,392,459	138,729
Accrued interest payable	85,581	45,617
Fair Value | Level 1 | U.S. Treasury securities
Assets
Total held to maturity debt securities	66,182	65,889
Fair Value | Level 2
Assets
Federal reserve bank and federal home loan bank stock	547,686	238,056
Liabilities
Deposits with stated maturities	11,040,582	9,443,253
Long-term borrowings	2,110,305	1,395,991
Junior subordinated debentures issued to capital trusts	55,042	50,923
Fair Value | Level 2 | U.S. government agency securities
Assets
Total held to maturity debt securities	255,640	212,712
Fair Value | Level 2 | Obligations of states and political subdivisions
Assets
Total held to maturity debt securities	452,919	453,195
Fair Value | Level 2 | Residential mortgage-backed securities
Assets
Total held to maturity debt securities	2,525,568	2,495,797
Fair Value | Level 2 | Trust preferred securities
Assets
Total held to maturity debt securities	29,992	31,106
Fair Value | Level 2 | Corporate and other debt securities
Assets
Total held to maturity debt securities	70,183	70,771
Fair Value | Level 3
Assets
Equity securities	16,342	15,138
Net loans	$ 47,389,743	$ 44,910,049