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INVESTMENT SECURITIES - Amortized Cost and Fair Value of HTM Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2026	Mar. 31, 2026	Dec. 31, 2025	Jun. 30, 2025	Mar. 31, 2025	Dec. 31, 2024
Debt Securities, Held-to-maturity, Fair Value to Amortized Cost [Abstract]
Amortized Cost	$ 1,572,334		$ 1,554,759
Gross Unrealized Gains	1,207		1,423
Gross Unrealized Losses	(136,459)		(116,210)
Fair Value	1,437,082		1,439,972
Allowance for credit losses	(787)	$ (749)	(744)	$ (704)	$ (701)	$ (704)
Total held-to-maturity, net of allowance for credit losses	1,571,547		1,554,015
Traditional securities
Debt Securities, Held-to-maturity, Fair Value to Amortized Cost [Abstract]
Amortized Cost	441,466		476,991
Gross Unrealized Gains	1,207		1,423
Gross Unrealized Losses	(31,381)		(29,000)
Fair Value	411,292		449,414
Allowance for credit losses	(38)		(41)
Total held-to-maturity, net of allowance for credit losses	441,428		476,950
GSE certificates & CMOs
Debt Securities, Held-to-maturity, Fair Value to Amortized Cost [Abstract]
Amortized Cost	181,708		184,690
Gross Unrealized Gains	905		1,178
Gross Unrealized Losses	(14,462)		(13,611)
Fair Value	168,151		172,257
Non-GSE certificates & CMOs
Debt Securities, Held-to-maturity, Fair Value to Amortized Cost [Abstract]
Amortized Cost	66,930		69,198
Gross Unrealized Gains	1		1
Gross Unrealized Losses	(3,791)		(3,331)
Fair Value	63,140		65,868
Asset-Backed Securities ("ABS")
Debt Securities, Held-to-maturity, Fair Value to Amortized Cost [Abstract]
Amortized Cost	126,409		156,020
Gross Unrealized Gains	16		9
Gross Unrealized Losses	(4,790)		(4,167)
Fair Value	121,635		151,862
Municipal
Debt Securities, Held-to-maturity, Fair Value to Amortized Cost [Abstract]
Amortized Cost	63,419		64,083
Gross Unrealized Gains	285		229
Gross Unrealized Losses	(8,276)		(7,891)
Fair Value	55,428		56,421
Corporate
Debt Securities, Held-to-maturity, Fair Value to Amortized Cost [Abstract]
Amortized Cost	3,000		3,000
Gross Unrealized Gains	0		6
Gross Unrealized Losses	(62)		0
Fair Value	2,938		3,006
Property Assessed Clean Energy ("PACE") assessments
Debt Securities, Held-to-maturity, Fair Value to Amortized Cost [Abstract]
Amortized Cost	1,130,868		1,077,768
Gross Unrealized Gains	0		0
Gross Unrealized Losses	(105,078)		(87,210)
Fair Value	1,025,790		990,558
Allowance for credit losses	(749)		(703)
Total held-to-maturity, net of allowance for credit losses	1,130,119		1,077,065
Commercial PACE assessments
Debt Securities, Held-to-maturity, Fair Value to Amortized Cost [Abstract]
Amortized Cost	365,470		327,735
Gross Unrealized Gains	0		0
Gross Unrealized Losses	(31,797)		(28,865)
Fair Value	333,673		298,870
Allowance for credit losses	(366)	(335)	(328)	(278)	(271)	(268)
Residential PACE assessments
Debt Securities, Held-to-maturity, Fair Value to Amortized Cost [Abstract]
Amortized Cost	765,398		750,033
Gross Unrealized Gains	0		0
Gross Unrealized Losses	(73,281)		(58,345)
Fair Value	692,117		691,688
Allowance for credit losses	$ (383)	$ (374)	$ (375)	$ (379)	$ (383)	$ (387)