Fair Value - Estimated fair value and related carrying amount, of the Company's financial instruments (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Financial assets:
Trading securities	$ 87,103		$ 31,321
SBA servicing asset	6,100		6,000
Financial liabilities:
Other derivative financial instruments (mortgage banking related)	(198,292)	$ 217,735
Carrying Amount
Financial assets:
Cash and cash equivalents	1,212,679		998,877
Trading securities	87,103		31,321
Investment securities	7,077,128		7,463,871
Mortgage loans held for sale	287,043		50,888
Loans, net of allowance for credit losses	33,080,211		31,931,916
Accrued interest receivable	165,533		154,400
Mortgage servicing rights	83,512		85,164
SBA servicing asset	6,079		5,952
Interest rate swap - non-designated hedge	194,037		169,180
Other derivative financial instruments (mortgage banking related)	$ 1,685		$ 3,759
Derivative Asset, Statement of Financial Position [Extensible Enumeration]	Derivative Asset, Noncurrent		Derivative Asset, Noncurrent
Financial liabilities:
Noninterest-bearing	$ 10,376,531		$ 10,649,274
Interest-bearing other than time deposits	22,607,022		22,149,682
Time deposits	4,654,642		4,249,953
Federal funds purchased and securities sold under agreements to repurchase	538,322		489,185
Corporate and subordinated debentures	391,626		391,904
Other borrowings	300,000		100,000
Accrued interest payable	52,625		56,808
Interest rate swap - non-designated hedge	605,918		803,539
Other derivative financial instruments (mortgage banking related)			947
Other derivative financial instruments (mortgage banking related)	276
Fair Value
Financial assets:
Cash and cash equivalents	1,212,679		998,877
Trading securities	87,103		31,321
Investment securities	6,739,567		7,061,167
Mortgage loans held for sale	287,043		50,888
Loans, net of allowance for credit losses	31,879,975		30,709,513
Accrued interest receivable	165,533		154,400
Mortgage servicing rights	83,512		85,164
SBA servicing asset	6,079		5,952
Interest rate swap - non-designated hedge	194,037		169,180
Other derivative financial instruments (mortgage banking related)	1,685		3,759
Financial liabilities:
Noninterest-bearing	10,376,531		10,649,274
Interest-bearing other than time deposits	22,607,022		22,149,682
Time deposits	4,636,870		4,208,498
Federal funds purchased and securities sold under agreements to repurchase	538,322		489,185
Corporate and subordinated debentures	390,833		388,909
Other borrowings	300,000		100,000
Accrued interest payable	52,625		56,808
Interest rate swap - non-designated hedge	605,918		803,539
Other derivative financial instruments (mortgage banking related)			947
Other derivative financial instruments (mortgage banking related)	276
Quoted Prices In Active Markets for Identical Assets (Level 1)
Financial assets:
Cash and cash equivalents	1,212,679		998,877
Investment securities	201,569		192,043
Significant Other Observable Inputs (Level 2)
Financial assets:
Trading securities	87,103		31,321
Investment securities	6,528,109		6,869,124
Mortgage loans held for sale	287,043		50,888
Accrued interest receivable	24,818		26,706
Interest rate swap - non-designated hedge	194,037		169,180
Other derivative financial instruments (mortgage banking related)	1,685		3,759
Financial liabilities:
Noninterest-bearing	10,376,531		10,649,274
Interest-bearing other than time deposits	22,607,022		22,149,682
Time deposits	4,636,870		4,208,498
Federal funds purchased and securities sold under agreements to repurchase	538,322		489,185
Corporate and subordinated debentures	390,833		388,909
Other borrowings	300,000		100,000
Accrued interest payable	52,625		56,808
Interest rate swap - non-designated hedge	605,918		803,539
Other derivative financial instruments (mortgage banking related)			947
Other derivative financial instruments (mortgage banking related)	276
Significant Unobservable Inputs (Level 3)
Financial assets:
Investment securities	9,889
Loans, net of allowance for credit losses	31,879,975		30,709,513
Accrued interest receivable	140,715		127,694
Mortgage servicing rights	83,512		85,164
SBA servicing asset	$ 6,079		$ 5,952