Fair Value - Estimated fair value and related carrying amount, of the Company's financial instruments (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Financial assets:
Trading securities	$ 88,088		$ 77,689
SBA servicing assets	6,400
Financial liabilities:
Other derivative financial instruments (mortgage banking related)	252,666	$ (286,881)
Carrying Amount
Financial assets:
Cash and cash equivalents	4,722,099		6,843,147
Trading securities	88,088		77,689
Investment securities	8,652,288		7,173,947
Loans held for sale	73,880		191,723
Loans, net of allowance for credit losses	27,615,558		23,626,359
Accrued interest receivable	109,995		90,069
Mortgage servicing rights	87,463		65,620
SBA servicing assets	6,449
Interest rate swap - non-designated hedge	666,470		408,776
Other derivative financial instruments (mortgage banking related)	1,854		5,966
Financial liabilities:
Deposits	38,875,851		35,054,829
Federal funds purchased and securities sold under agreements to repurchase	669,999		781,239
Other borrowings	392,460		327,066
Accrued interest payable	4,192		3,345
Interest rate swap - non-designated hedge	666,503		410,137
Other derivative financial instruments (mortgage banking related)	299
Fair Value
Financial assets:
Cash and cash equivalents	4,722,099		6,843,147
Trading securities	88,088		77,689
Investment securities	8,338,509		7,132,110
Loans held for sale	73,880		191,723
Loans, net of allowance for credit losses	27,644,893		23,921,372
Accrued interest receivable	109,995		90,069
Mortgage servicing rights	87,463		65,620
Interest rate swap - non-designated hedge	666,470		408,776
Other derivative financial instruments (mortgage banking related)	1,854		5,966
Financial liabilities:
Deposits	38,813,989		35,050,516
Federal funds purchased and securities sold under agreements to repurchase	669,999		781,239
Other borrowings	375,593		334,640
Accrued interest payable	4,192		3,345
Interest rate swap - non-designated hedge	666,503		410,137
Other derivative financial instruments (mortgage banking related)	299
Commitments to extend credit | Fair Value
Financial liabilities:
Commitments to extend credit	10,888		93,501
Quoted Prices In Active Markets for Identical Assets (Level 1)
Financial assets:
Cash and cash equivalents	4,722,099		6,843,147
Investment securities	179,815		160,568
Significant Other Observable Inputs (Level 2)
Financial assets:
Trading securities	88,088		77,689
Investment securities	8,158,694		6,971,542
Loans held for sale	73,880		191,723
Accrued interest receivable	27,601		19,241
Interest rate swap - non-designated hedge	666,470		408,776
Other derivative financial instruments (mortgage banking related)	1,854		5,966
Financial liabilities:
Deposits	38,813,989		35,050,516
Federal funds purchased and securities sold under agreements to repurchase	669,999		781,239
Other borrowings	375,593		334,640
Accrued interest payable	4,192		3,345
Interest rate swap - non-designated hedge	666,503		410,137
Other derivative financial instruments (mortgage banking related)	299
Significant Other Observable Inputs (Level 2) | Commitments to extend credit
Financial liabilities:
Commitments to extend credit	10,888		93,501
Significant Unobservable Inputs (Level 3)
Financial assets:
Loans, net of allowance for credit losses	27,644,893		23,921,372
Accrued interest receivable	82,394		70,828
Mortgage servicing rights	87,463		$ 65,620
SBA servicing assets	$ 6,449