Fair Value - Estimated fair value and related carrying amount, of the Company's financial instruments (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Financial assets:
Trading securities	$ 92,161		$ 31,321
SBA servicing asset	6,300		6,000
Financial liabilities:
Other derivative financial instruments (mortgage banking related)	150,861	$ (58,426)
Carrying Amount
Financial assets:
Cash and cash equivalents	1,117,166		998,877
Trading securities	92,161		31,321
Investment securities	7,048,308		7,463,871
Loans held for sale	100,007		50,888
Loans, net of allowance for credit losses	32,762,266		31,931,916
Accrued interest receivable	159,862		154,400
Mortgage servicing rights	88,904		85,164
SBA servicing asset	6,307		5,952
Interest rate swap - non-designated hedge	182,802		169,180
Other derivative financial instruments (mortgage banking related)	$ 2,234		$ 3,759
Derivative Asset, Statement of Financial Position [Extensible Enumeration]	Derivative Asset, Noncurrent		Derivative Asset, Noncurrent
Financial liabilities:
Noninterest-bearing	$ 10,374,464		$ 10,649,274
Interest-bearing other than time deposits	22,144,872		22,149,682
Time deposits	4,579,066		4,249,953
Federal funds purchased and securities sold under agreements to repurchase	542,403		489,185
Corporate and subordinated debentures	391,719		391,904
Other borrowings	300,000		100,000
Accrued interest payable	55,343		56,808
Interest rate swap - non-designated hedge	955,347		803,539
Other derivative financial instruments (mortgage banking related)			947
Fair Value
Financial assets:
Cash and cash equivalents	1,117,166		998,877
Trading securities	92,161		31,321
Investment securities	6,620,721		7,061,167
Loans held for sale	100,007		50,888
Loans, net of allowance for credit losses	31,609,083		30,709,513
Accrued interest receivable	159,862		154,400
Mortgage servicing rights	88,904		85,164
SBA servicing asset	6,307		5,952
Interest rate swap - non-designated hedge	182,802		169,180
Other derivative financial instruments (mortgage banking related)	2,234		3,759
Financial liabilities:
Noninterest-bearing	10,374,464		10,649,274
Interest-bearing other than time deposits	22,144,872		22,149,682
Time deposits	4,540,610		4,208,498
Federal funds purchased and securities sold under agreements to repurchase	542,403		489,185
Corporate and subordinated debentures	385,136		388,909
Other borrowings	300,000		100,000
Accrued interest payable	55,343		56,808
Interest rate swap - non-designated hedge	955,347		803,539
Other derivative financial instruments (mortgage banking related)			947
Quoted Prices In Active Markets for Identical Assets (Level 1)
Financial assets:
Cash and cash equivalents	1,117,166		998,877
Investment securities	201,516		192,043
Significant Other Observable Inputs (Level 2)
Financial assets:
Trading securities	92,161		31,321
Investment securities	6,419,205		6,869,124
Loans held for sale	100,007		50,888
Accrued interest receivable	25,803		26,706
Interest rate swap - non-designated hedge	182,802		169,180
Other derivative financial instruments (mortgage banking related)	2,234		3,759
Financial liabilities:
Noninterest-bearing	10,374,464		10,649,274
Interest-bearing other than time deposits	22,144,872		22,149,682
Time deposits	4,540,610		4,208,498
Federal funds purchased and securities sold under agreements to repurchase	542,403		489,185
Corporate and subordinated debentures	385,136		388,909
Other borrowings	300,000		100,000
Accrued interest payable	55,343		56,808
Interest rate swap - non-designated hedge	955,347		803,539
Other derivative financial instruments (mortgage banking related)			947
Significant Unobservable Inputs (Level 3)
Financial assets:
Loans, net of allowance for credit losses	31,609,083		30,709,513
Accrued interest receivable	134,059		127,694
Mortgage servicing rights	88,904		85,164
SBA servicing asset	$ 6,307		$ 5,952