INVESTMENT SECURITIES - Summary of Amortized Cost and Fair Value (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Securities held-to-maturity:
Amortized Cost	$ 329,381	$ 0
Gross Unrealized Gains	0
Gross Unrealized Losses	(18,429)
Fair Value	310,952
Securities available-for-sale:
Amortized Cost	909,280	1,304,723
Gross Unrealized Gains	5,138	18,324
Gross Unrealized Losses	(15,643)	(7,344)
Securities available-for-sale, at fair value	898,775	1,315,703
U.S. government agency and U.S. government sponsored enterprise residential mortgage-backed securities
Securities held-to-maturity:
Amortized Cost	153,713
Gross Unrealized Gains	0
Gross Unrealized Losses	(7,832)
Fair Value	145,881
Securities available-for-sale:
Amortized Cost	12,084	190,382
Gross Unrealized Gains	0	2,898
Gross Unrealized Losses	(351)	(1,311)
Securities available-for-sale, at fair value	11,733	191,969
U.S. government agency and U.S. government sponsored enterprise collateralized mortgage obligations
Securities held-to-maturity:
Amortized Cost	61,464
Gross Unrealized Gains	0
Gross Unrealized Losses	(3,646)
Fair Value	57,818
Securities available-for-sale:
Amortized Cost	170,827	242,458
Gross Unrealized Gains	438	1,171
Gross Unrealized Losses	(5,050)	(2,088)
Securities available-for-sale, at fair value	166,215	241,541
Municipal securities
Securities held-to-maturity:
Amortized Cost	114,204
Gross Unrealized Gains	0
Gross Unrealized Losses	(6,951)
Fair Value	107,253
Securities available-for-sale:
Amortized Cost		117,913
Gross Unrealized Gains		2,641
Gross Unrealized Losses		(1,539)
Securities available-for-sale, at fair value		119,015
SBA loan pool securities
Securities available-for-sale:
Amortized Cost	13,918	14,679
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(108)	(88)
Securities available-for-sale, at fair value	13,810	14,591
Non-agency residential mortgage-backed securities
Securities available-for-sale:
Amortized Cost	54,417	56,014
Gross Unrealized Gains	0	11
Gross Unrealized Losses	(3,955)	0
Securities available-for-sale, at fair value	50,462	56,025
Collateralized loan obligations
Securities available-for-sale:
Amortized Cost	492,775	521,275
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(4,802)	(2,311)
Securities available-for-sale, at fair value	487,973	518,964
Corporate debt securities
Securities available-for-sale:
Amortized Cost	165,259	162,002
Gross Unrealized Gains	4,700	11,603
Gross Unrealized Losses	(1,377)	(7)
Securities available-for-sale, at fair value	$ 168,582	$ 173,598

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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