INVESTMENT SECURITIES - Schedule of Unrealized Losses on Available for Sale Securities and Held-to-Maturity Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2025	Dec. 31, 2024
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Available for sale, less than 12 months, fair value	$ 344,099	$ 206,050
Available for sale, less than 12 months, unrealized losses	1,543	1,373
Available for sale, 12 months or longer, fair value	581,740	648,913
Available for sale, 12 months or longer, unrealized losses	55,323	71,297
Available for sale, total fair value	925,839	854,963
Available for sale, total unrealized losses	56,866	72,670
GSE certificates & CMOs
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Available for sale, less than 12 months, fair value	57,455	50,828
Available for sale, less than 12 months, unrealized losses	264	881
Available for sale, 12 months or longer, fair value	209,465	249,736
Available for sale, 12 months or longer, unrealized losses	23,772	30,346
Available for sale, total fair value	266,920	300,564
Available for sale, total unrealized losses	24,036	31,227
Non-GSE certificates & CMOs
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Available for sale, less than 12 months, fair value	24,613	33,778
Available for sale, less than 12 months, unrealized losses	1	71
Available for sale, 12 months or longer, fair value	139,036	145,329
Available for sale, 12 months or longer, unrealized losses	12,368	15,510
Available for sale, total fair value	163,649	179,107
Available for sale, total unrealized losses	12,369	15,581
Asset-Backed Securities ("ABS")
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Available for sale, less than 12 months, fair value	247,404	121,444
Available for sale, less than 12 months, unrealized losses	1,050	421
Available for sale, 12 months or longer, fair value	139,660	151,668
Available for sale, 12 months or longer, unrealized losses	12,276	14,142
Available for sale, total fair value	387,064	273,112
Available for sale, total unrealized losses	13,326	14,563
Corporate
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Available for sale, less than 12 months, fair value	0	0
Available for sale, less than 12 months, unrealized losses	0	0
Available for sale, 12 months or longer, fair value	93,579	98,315
Available for sale, 12 months or longer, unrealized losses	6,907	11,167
Available for sale, total fair value	93,579	98,315
Available for sale, total unrealized losses	6,907	11,167
Other
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Available for sale, less than 12 months, fair value	14,627	0
Available for sale, less than 12 months, unrealized losses	228	0
Available for sale, 12 months or longer, fair value	0	3,865
Available for sale, 12 months or longer, unrealized losses	0	132
Available for sale, total fair value	14,627	3,865
Available for sale, total unrealized losses	$ 228	$ 132

Amalgamated Financial Corp. 10-Q