INVESTMENT SECURITIES - Amortized Cost and Fair Value of AFS Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	$ 1,621,169	$ 1,585,334
Gross Unrealized Gains	1,554	539
Gross Unrealized Losses	(94,672)	(102,831)
Fair Value	1,528,051	1,483,042
Traditional securities
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	1,539,887	1,532,471
Gross Unrealized Gains	578	99
Gross Unrealized Losses	(94,672)	(102,832)
Fair Value	1,445,793	1,429,739
Government sponsored entities ("GSE") residential CMOs ("collateralized mortgage obligations")
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	503,557	521,101
Gross Unrealized Gains	263	59
Gross Unrealized Losses	(38,032)	(40,545)
Fair Value	465,788	480,615
Non-GSE certificates & CMOs
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	206,361	218,550
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(19,908)	(21,690)
Fair Value	186,453	196,860
ABS
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	685,746	648,585
Gross Unrealized Gains	315	40
Gross Unrealized Losses	(17,771)	(20,990)
Fair Value	668,290	627,635
Corporate
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	140,026	140,038
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(18,653)	(19,297)
Fair Value	121,373	120,741
Other
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	4,197	4,197
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(308)	(309)
Fair Value	3,889	3,888
Property Assessed Clean Energy ("PACE") assessments
Debt Securities, Available-for-Sale [Line Items]
Fair Value	82,258	53,303
Residential PACE assessments
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	81,282	52,863
Gross Unrealized Gains	976	440
Gross Unrealized Losses	0	0
Fair Value	$ 82,258	$ 53,303