FAIR VALUE MEASURES - Carrying Amount and Estimated Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Financial assets:
Cash and due from banks	$ 284,567	$ 307,813
Federal funds sold and interest-bearing accounts	0	20,000
Debt securities held-to-maturity	114,538	78,206
Financial liabilities:
Other borrowings	1,875,736	739,879
Subordinated deferrable interest debentures	128,322	126,328
Carrying Amount
Financial assets:
Cash and due from banks	284,567	307,813
Federal funds sold and interest-bearing accounts	833,565	3,756,844
Time deposits in other banks		0
Debt securities held-to-maturity	134,864
Loans, net	19,617,604	15,662,495
Accrued interest receivable	77,042	56,917
Financial liabilities:
Deposits	19,462,738	19,665,553
Securities sold under agreements to repurchase		5,845
Other borrowings	1,875,736	739,879
Subordinated deferrable interest debentures	128,322	126,328
Accrued interest payable	10,530	4,313
Fair Value
Financial assets:
Cash and due from banks	284,567	307,813
Federal funds sold and interest-bearing accounts	833,565	3,756,844
Time deposits in other banks		0
Debt securities held-to-maturity	114,538
Loans, net	19,067,612	15,509,410
Accrued interest receivable	77,042	56,917
Financial liabilities:
Deposits	19,455,187	19,667,612
Securities sold under agreements to repurchase		5,845
Other borrowings	1,861,850	760,829
Subordinated deferrable interest debentures	125,988	117,764
Accrued interest payable	10,530	4,313
Fair Value | Level 1
Financial assets:
Cash and due from banks	284,567	307,813
Federal funds sold and interest-bearing accounts	833,565	3,756,844
Time deposits in other banks		0
Debt securities held-to-maturity	0
Loans, net	0	0
Accrued interest receivable	0	0
Financial liabilities:
Deposits	0	0
Securities sold under agreements to repurchase		5,845
Other borrowings	0	0
Subordinated deferrable interest debentures	0	0
Accrued interest payable	0	0
Fair Value | Level 2
Financial assets:
Cash and due from banks	0	0
Federal funds sold and interest-bearing accounts	0	0
Time deposits in other banks		0
Debt securities held-to-maturity	114,538
Loans, net	0	0
Accrued interest receivable	7,694	2,373
Financial liabilities:
Deposits	19,455,187	19,667,612
Securities sold under agreements to repurchase		0
Other borrowings	1,861,850	760,829
Subordinated deferrable interest debentures	125,988	117,764
Accrued interest payable	10,530	4,313
Fair Value | Level 3
Financial assets:
Cash and due from banks	0	0
Federal funds sold and interest-bearing accounts	0	0
Time deposits in other banks		0
Debt securities held-to-maturity
Loans, net	19,067,612	15,509,410
Accrued interest receivable	69,348	54,544
Financial liabilities:
Deposits	0	0
Securities sold under agreements to repurchase		0
Other borrowings	0	0
Subordinated deferrable interest debentures	0	0
Accrued interest payable	$ 0	$ 0