FAIR VALUE - Fair Value (Detail) - USD ($) $ in Thousands	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021
Assets:
Investment securities available for sale	$ 5,433,369		$ 5,599,520
Held To Maturity Securities Amortized	424,726		437,537
Less: allowance for credit losses on held to maturity securities	(8,401)		(8,286)
Investment securities held to maturity, net of ACL	416,325		429,251
Loans held for investment, net of ACL	11,452,257		11,292,361
Mortgage servicing rights	28,034	$ 28,431	29,037	$ 30,277	$ 30,753	$ 30,986
Advances from the FHLB:
Short-term	0		475,000
Long-term	500,000		200,000
Other long-term borrowings	161,700		183,762
Carrying Reported Amount Fair Value Disclosure [Member]
Assets:
Cash and due from banks and money market investments	1,047,534		480,505
Investment securities available for sale	5,433,369		5,599,520
Held To Maturity Securities Amortized	424,726		437,537
Less: allowance for credit losses on held to maturity securities	(8,401)		(8,286)
Investment securities held to maturity, net of ACL	416,325		429,251
Equity securities	43,210		50,428
Other investment securities	4,891		4,861
Loans held for sale	14,295		12,306
Total gross loans held for investment portfolio	11,719,315		11,552,825
ACL for loans and finance leases	(267,058)		(260,464)
Loans held for investment, net of ACL	11,452,257		11,292,361
Mortgage servicing rights	28,034		29,037
Derivative Assets	494		633
Financial Instruments Financial Liabilities Balance Sheet Groupings [Abstract]
Deposits	16,819,692		16,143,467
Short-term securities sold under agreements to repurchase (amortized cost)	73,934		75,133
Advances from the FHLB:
Short-term			475,000
Long-term	500,000		200,000
Other long-term borrowings	161,700		183,762
Derivative Liabilities	357		476
Federal Home Loan Bank Stock	34,700		42,900
Estimate Of Fair Value Fair Value Disclosure [Member]
Assets:
Cash and due from banks and money market investments	1,047,534		480,505
Investment securities available for sale	5,433,369		5,599,520
Investment securities held to maturity, net of ACL	410,181		427,115
Equity securities	43,210		50,428
Other investment securities	4,891		4,861
Loans held for sale	14,295		12,306
Loans held for investment, net of ACL	11,256,830		11,106,809
Mortgage servicing rights	44,420		44,710
Derivative Assets	494		633
Financial Instruments Financial Liabilities Balance Sheet Groupings [Abstract]
Deposits	16,820,272		16,139,937
Short-term securities sold under agreements to repurchase (amortized cost)	74,030		75,230
Advances from the FHLB:
Short-term			474,731
Long-term	495,589		199,865
Other long-term borrowings	162,983		187,246
Derivative Liabilities	357		476
Estimate Of Fair Value Fair Value Disclosure [Member] | Fair Value Inputs Level 1 [Member]
Assets:
Cash and due from banks and money market investments	1,047,534		480,505
Investment securities available for sale	139,669		138,875
Investment securities held to maturity, net of ACL	0		0
Equity securities	0		0
Other investment securities	4,891		4,861
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
Short-term securities sold under agreements to repurchase (amortized cost)	0		0
Advances from the FHLB:
Short-term			0
Long-term	0		0
Other long-term 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	5,286,343		5,452,150
Investment securities held to maturity, net of ACL	244,521		260,106
Equity securities	43,210		50,428
Other investment securities	0		0
Loans held for sale	14,295		12,306
Loans held for investment, net of ACL	0		0
Mortgage servicing rights	0		0
Derivative Assets	494		633
Financial Instruments Financial Liabilities Balance Sheet Groupings [Abstract]
Deposits	16,820,272		16,139,937
Short-term securities sold under agreements to repurchase (amortized cost)	74,030		75,230
Advances from the FHLB:
Short-term			474,731
Long-term	495,589		199,865
Other long-term borrowings	0		0
Derivative Liabilities	357		476
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	7,357		8,495
Investment securities held to maturity, net of ACL	165,660		167,009
Equity securities	0		0
Other investment securities	0		0
Loans held for sale	0		0
Loans held for investment, net of ACL	11,256,830		11,106,809
Mortgage servicing rights	44,420		44,710
Derivative Assets	0		0
Financial Instruments Financial Liabilities Balance Sheet Groupings [Abstract]
Deposits	0		0
Short-term securities sold under agreements to repurchase (amortized cost)	0		0
Advances from the FHLB:
Short-term			0
Long-term	0		0
Other long-term borrowings	162,983		187,246
Derivative Liabilities	$ 0		$ 0