Fair Value - Estimated fair value and related carrying amount, of the Company's financial instruments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Financial assets:
Trading securities	$ 31,321	$ 31,263
SBA servicing asset	6,000	6,100
Financial liabilities:
Other borrowings	491,904
Other derivative financial instruments (mortgage banking related)	(229,657)	741,583	$ (516,271)
Carrying Amount
Financial assets:
Cash and cash equivalents	998,877	1,312,563
Trading securities	31,321	31,263
Investment securities	7,463,871	8,189,780
Loans held for sale	50,888	28,968
Loans, net of allowance for credit losses	31,931,916	29,821,418
Accrued interest receivable	154,400	134,594
Mortgage servicing rights	85,164	86,610
SBA servicing asset	5,952	6,068
Interest rate swap - non-designated hedge	169,180	210,216
Other derivative financial instruments (mortgage banking related)	$ 3,759	$ 800
Derivative Asset, Statement of Financial Position [Extensible Enumeration]	Derivative Asset, Noncurrent	Derivative Asset, Noncurrent
Financial liabilities:
Noninterest-bearing	$ 10,649,274	$ 13,168,656
Interest-bearing other than time deposits	22,149,682	20,761,981
Time deposits	4,249,953	2,419,986
Federal funds purchased and securities sold under agreements to repurchase	489,185	556,417
Corporate and subordinated debentures	391,904
Other borrowings	100,000	392,275
Accrued interest payable	56,808	6,218
Interest rate swap - non-designated hedge	803,539	1,033,980
Other derivative financial instruments (mortgage banking related)	947	163
Fair Value
Financial assets:
Cash and cash equivalents	998,877	1,312,563
Trading securities	31,321	31,263
Investment securities	7,061,167	7,756,707
Loans held for sale	50,888	28,968
Loans, net of allowance for credit losses	30,709,513	29,329,499
Accrued interest receivable	154,400	134,594
Mortgage servicing rights	85,164	86,610
SBA servicing asset	5,952
Interest rate swap - non-designated hedge	169,180	210,216
Other derivative financial instruments (mortgage banking related)	$ 3,759	$ 800
Derivative Asset, Statement of Financial Position [Extensible Enumeration]	Derivative Asset, Noncurrent	Derivative Asset, Noncurrent
Financial liabilities:
Noninterest-bearing	$ 10,649,274	$ 13,168,656
Interest-bearing other than time deposits	22,149,682	20,761,981
Time deposits	4,208,498	2,333,764
Federal funds purchased and securities sold under agreements to repurchase	489,185	556,417
Corporate and subordinated debentures	388,909
Other borrowings	100,000	377,360
Accrued interest payable	56,808	6,218
Interest rate swap - non-designated hedge	803,539	1,033,980
Other derivative financial instruments (mortgage banking related)	947	163
Quoted Prices In Active Markets for Identical Assets (Level 1)
Financial assets:
Cash and cash equivalents	998,877	1,312,563
Investment securities	192,043	179,717
Significant Other Observable Inputs (Level 2)
Financial assets:
Trading securities	31,321	31,263
Investment securities	6,869,124	7,576,990
Loans held for sale	50,888	28,968
Accrued interest receivable	26,706	28,449
Interest rate swap - non-designated hedge	169,180	210,216
Other derivative financial instruments (mortgage banking related)	$ 3,759	$ 800
Derivative Asset, Statement of Financial Position [Extensible Enumeration]	Derivative Asset, Noncurrent	Derivative Asset, Noncurrent
Financial liabilities:
Noninterest-bearing	$ 10,649,274	$ 13,168,656
Interest-bearing other than time deposits	22,149,682	20,761,981
Time deposits	4,208,498	2,333,764
Federal funds purchased and securities sold under agreements to repurchase	489,185	556,417
Corporate and subordinated debentures	388,909
Other borrowings	100,000	377,360
Accrued interest payable	56,808	6,218
Interest rate swap - non-designated hedge	803,539	1,033,980
Other derivative financial instruments (mortgage banking related)	947	163
Significant Unobservable Inputs (Level 3)
Financial assets:
Loans, net of allowance for credit losses	30,709,513	29,329,499
Accrued interest receivable	127,694	106,145
Mortgage servicing rights	85,164	86,610
SBA servicing asset	$ 5,952	$ 6,068