FAIR VALUE - Fair Value (Detail) - USD ($) $ in Thousands	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020
Assets:
Investment securities available for sale	$ 6,081,120		$ 6,453,761
Held To Maturity Securities Amortized	458,227
Less: allowance for credit losses on held to maturity securities	(8,885)		(8,571)
Investment securities held to maturity, net of ACL	449,342		169,562
Less: ACL for loans and finance leases	(252,152)	$ (245,447)	(269,030)	$ (324,958)	$ (358,936)	$ (385,887)
Loans held for investment, net of ACL	10,954,722		10,791,628
Mortgage servicing rights	30,277	$ 30,753	30,986	$ 32,335	$ 32,710	$ 33,071
Financial Instruments Financial Liabilities Balance Sheet Groupings [Abstract]
Other borrowings	183,762		183,762
Carrying Reported Amount Fair Value Disclosure [Member]
Assets:
Cash and due from banks and money market investments	1,263,523		2,543,058
Investment securities available for sale	6,081,120		6,453,761
Held To Maturity Securities Amortized	458,227		178,133
Less: allowance for credit losses on held to maturity securities	(8,885)		(8,571)
Investment securities held to maturity, net of ACL	449,342		169,562
Equity Securities	27,761		26,791
Other investment securities	5,082		5,378
Loans held for sale	22,601		35,155
Total gross loans held for investment portfolio	11,206,874		11,060,658
Less: ACL for loans and finance leases	(252,152)		(269,030)
Loans held for investment, net of ACL	10,954,722		10,791,628
Mortgage servicing rights	30,277		30,986
Derivative Assets	1,025		1,505
Financial Instruments Financial Liabilities Balance Sheet Groupings [Abstract]
Deposits	17,140,128		17,784,894
Securities sold under agreements to repurchase	200,000		300,000
Advances from FHLB	200,000		200,000
Other borrowings	183,762		183,762
Derivative Liabilities	636		1,178
Federal Home Loan Bank Stock	21,300		21,500
Estimate Of Fair Value Fair Value Disclosure [Member]
Assets:
Cash and due from banks and money market investments	1,263,523		2,543,058
Investment securities available for sale	6,081,120		6,453,761
Investment securities held to maturity, net of ACL	453,242		167,147
Equity Securities	27,761		26,791
Other investment securities	5,082		5,378
Loans held for sale	22,790		36,147
Loans held for investment, net of ACL	10,954,724		10,900,400
Mortgage servicing rights	44,337		42,132
Derivative Assets	1,025		1,505
Financial Instruments Financial Liabilities Balance Sheet Groupings [Abstract]
Deposits	17,146,043		17,800,706
Securities sold under agreements to repurchase	205,456		322,105
Advances from FHLB	200,051		202,044
Other borrowings	175,122		177,689
Derivative Liabilities	636		1,178
Estimate Of Fair Value Fair Value Disclosure [Member] | Fair Value Inputs Level 1 [Member]
Assets:
Cash and due from banks and money market investments	1,263,523		2,543,058
Investment securities available for sale	141,347		148,486
Investment securities held to maturity, net of ACL	0		0
Equity Securities	0		0
Other investment securities	5,082		5,378
Loans held for sale	0		0
Loans held for investment, net of ACL	0		0
Mortgage servicing rights	0		0
Derivative Assets	0		0
Financial Instruments Financial Liabilities Balance Sheet Groupings [Abstract]
Deposits	0		0
Securities sold under agreements to repurchase	0		0
Advances from FHLB	0		0
Other borrowings	0		0
Derivative Liabilities	0		0
Estimate Of Fair Value Fair Value Disclosure [Member] | Fair Value Inputs Level 2 [Member]
Assets:
Cash and due from banks and money market investments	0		0
Investment securities available for sale	5,929,593		6,294,191
Investment securities held to maturity, net of ACL	278,223		0
Equity Securities	27,761		26,791
Other investment securities	0		0
Loans held for sale	22,790		36,147
Loans held for investment, net of ACL	0		0
Mortgage servicing rights	0		0
Derivative Assets	1,025		1,505
Financial Instruments Financial Liabilities Balance Sheet Groupings [Abstract]
Deposits	17,146,043		17,800,706
Securities sold under agreements to repurchase	205,456		322,105
Advances from FHLB	200,051		202,044
Other borrowings	0		0
Derivative Liabilities	636		1,178
Estimate Of Fair Value Fair Value Disclosure [Member] | Fair Value Inputs Level 3 [Member]
Assets:
Cash and due from banks and money market investments	0		0
Investment securities available for sale	10,180		11,084
Investment securities held to maturity, net of ACL	175,019		167,147
Equity Securities	0		0
Other investment securities	0		0
Loans held for sale	0		0
Loans held for investment, net of ACL	10,954,724		10,900,400
Mortgage servicing rights	44,337		42,132
Derivative Assets	0		0
Financial Instruments Financial Liabilities Balance Sheet Groupings [Abstract]
Deposits	0		0
Securities sold under agreements to repurchase	0		0
Advances from FHLB	0		0
Other borrowings	175,122		177,689
Derivative Liabilities	$ 0		$ 0