Fair Value - Estimated fair value and related carrying amount, of the Company's financial instruments (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Jun. 30, 2022	Dec. 31, 2021
Financial assets:
Trading securities	$ 51,940			$ 77,689
SBA servicing assets			$ 7,000
Financial liabilities:
Other derivative financial instruments (mortgage banking related)	668,812	$ (319,824)
Carrying Amount
Financial assets:
Cash and cash equivalents	2,809,695			6,843,147
Trading securities	51,940			77,689
Investment securities	8,287,543			7,173,947
Loans held for sale	34,477			191,723
Loans, net of allowance for credit losses	28,511,905			23,626,359
Accrued interest receivable	124,553			90,069
Mortgage servicing rights	90,459			65,620
SBA servicing assets	6,981
Interest rate swap - non-designated hedge	1,081,768			408,776
Other derivative financial instruments (mortgage banking related)	$ 2,035			$ 5,966
Derivative Asset, Statement of Financial Position [Extensible Enumeration]	Derivative Asset, Noncurrent			Derivative Asset, Noncurrent
Financial liabilities:
Deposits	$ 37,666,021			$ 35,054,829
Federal funds purchased and securities sold under agreements to repurchase	557,802			781,239
Other borrowings	392,368			327,066
Accrued interest payable	6,354			3,345
Interest rate swap - non-designated hedge	1,081,267			410,137
Other derivative financial instruments (mortgage banking related)	1,681
Fair Value
Financial assets:
Cash and cash equivalents	2,809,695			6,843,147
Trading securities	51,940			77,689
Investment securities	7,848,527			7,132,110
Loans held for sale	34,477			191,723
Loans, net of allowance for credit losses	28,271,062			23,921,372
Accrued interest receivable	124,553			90,069
Mortgage servicing rights	90,459			65,620
Interest rate swap - non-designated hedge	1,081,768			408,776
Other derivative financial instruments (mortgage banking related)	2,035			5,966
Financial liabilities:
Deposits	37,578,773			35,050,516
Federal funds purchased and securities sold under agreements to repurchase	557,802			781,239
Other borrowings	379,992			334,640
Accrued interest payable	6,354			3,345
Interest rate swap - non-designated hedge	1,081,267			410,137
Other derivative financial instruments (mortgage banking related)	1,681
Commitments to extend credit | Fair Value
Financial liabilities:
Commitments to extend credit	(92,429)			93,501
Quoted Prices In Active Markets for Identical Assets (Level 1)
Financial assets:
Cash and cash equivalents	2,809,695			6,843,147
Investment securities	179,755			160,568
Significant Other Observable Inputs (Level 2)
Financial assets:
Trading securities	51,940			77,689
Investment securities	7,668,772			6,971,542
Loans held for sale	34,477			191,723
Accrued interest receivable	28,508			19,241
Interest rate swap - non-designated hedge	1,081,768			408,776
Other derivative financial instruments (mortgage banking related)	2,035			5,966
Financial liabilities:
Deposits	37,578,773			35,050,516
Federal funds purchased and securities sold under agreements to repurchase	557,802			781,239
Other borrowings	379,992			334,640
Accrued interest payable	6,354			3,345
Interest rate swap - non-designated hedge	1,081,267			410,137
Other derivative financial instruments (mortgage banking related)	1,681
Significant Other Observable Inputs (Level 2) | Commitments to extend credit
Financial liabilities:
Commitments to extend credit	(92,429)			93,501
Significant Unobservable Inputs (Level 3)
Financial assets:
Loans, net of allowance for credit losses	28,271,062			23,921,372
Accrued interest receivable	96,045			70,828
Mortgage servicing rights	90,459			$ 65,620
SBA servicing assets	$ 6,981