Fair Value Measurement of Assets and Liabilities - Carrying Amounts and Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Assets
Interest bearing deposits with banks	$ 1,844,764	$ 1,071,360
Equity securities	36,473	29,378
Investment securities held to maturity	2,660,605	2,227,612
Accrued interest receivable	96,882	106,230
Liabilities
Deposits with stated maturities	3,687,044	6,714,678
U.S. Treasury securities
Assets
Investment securities held to maturity	71,661	75,484
U.S. government agency securities
Assets
Investment securities held to maturity	6,378	6,513
Obligations of states and political subdivisions
Assets
Investment securities held to maturity	344,164	484,506
Residential mortgage-backed securities
Assets
Investment securities held to maturity	2,152,301	1,589,655
Trust preferred securities
Assets
Investment securities held to maturity	31,916	30,033
Corporate and other debt securities
Assets
Investment securities held to maturity	54,185	41,421
Carrying Amount
Assets
Investment securities held to maturity	2,668,697	2,173,011
Carrying Amount | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets
Cash and due from banks	205,156	257,845
Interest bearing deposits with banks	1,844,764	1,071,360
Accrued interest receivable	96,882	106,230
Liabilities
Deposits without stated maturities	31,945,368	25,220,924
Short-term borrowings	655,726	1,147,958
Accrued interest payable	4,909	18,839
Carrying Amount | Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Treasury securities
Assets
Investment securities held to maturity	67,558	68,126
Carrying Amount | Significant Other Observable  Inputs (Level 2)
Assets
Federal Reserve Bank and Federal Home Loan Bank stock	206,450	250,116
Liabilities
Deposits with stated maturities	3,687,044	6,714,678
Long-term borrowings	1,423,676	2,295,665
Junior subordinated debentures issued to capital trusts	56,413	56,065
Carrying Amount | Significant Other Observable  Inputs (Level 2) | U.S. government agency securities
Assets
Investment securities held to maturity	6,265	6,222
Carrying Amount | Significant Other Observable  Inputs (Level 2) | Obligations of states and political subdivisions
Assets
Investment securities held to maturity	337,962	470,259
Carrying Amount | Significant Other Observable  Inputs (Level 2) | Residential mortgage-backed securities
Assets
Investment securities held to maturity	2,166,142	1,550,306
Carrying Amount | Significant Other Observable  Inputs (Level 2) | Trust preferred securities
Assets
Investment securities held to maturity	37,020	37,348
Carrying Amount | Significant Other Observable  Inputs (Level 2) | Corporate and other debt securities
Assets
Investment securities held to maturity	53,750	40,750
Carrying Amount | Significant Unobservable Inputs (Level 3)
Assets
Equity securities	3,629	2,999
Net loans	33,794,455	31,876,869
Fair Value
Assets
Investment securities held to maturity	2,660,605	2,227,612
Fair Value | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets
Cash and due from banks	205,156	257,845
Interest bearing deposits with banks	1,844,764	1,071,360
Accrued interest receivable	96,882	106,230
Liabilities
Deposits without stated maturities	31,945,368	25,220,924
Short-term borrowings	637,490	1,151,478
Accrued interest payable	4,909	18,839
Fair Value | Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Treasury securities
Assets
Investment securities held to maturity	71,661	75,484
Fair Value | Significant Other Observable  Inputs (Level 2)
Assets
Federal Reserve Bank and Federal Home Loan Bank stock	206,450	250,116
Liabilities
Deposits with stated maturities	3,670,113	6,639,022
Long-term borrowings	1,404,184	2,405,345
Junior subordinated debentures issued to capital trusts	46,306	57,779
Fair Value | Significant Other Observable  Inputs (Level 2) | U.S. government agency securities
Assets
Investment securities held to maturity	6,378	6,513
Fair Value | Significant Other Observable  Inputs (Level 2) | Obligations of states and political subdivisions
Assets
Investment securities held to maturity	344,164	484,506
Fair Value | Significant Other Observable  Inputs (Level 2) | Residential mortgage-backed securities
Assets
Investment securities held to maturity	2,152,301	1,589,655
Fair Value | Significant Other Observable  Inputs (Level 2) | Trust preferred securities
Assets
Investment securities held to maturity	31,916	30,033
Fair Value | Significant Other Observable  Inputs (Level 2) | Corporate and other debt securities
Assets
Investment securities held to maturity	54,185	41,421
Fair Value | Significant Unobservable Inputs (Level 3)
Assets
Equity securities	3,629	2,999
Net loans	$ 33,283,251	$ 31,635,060