SECURITIES - Schedule of Securities Available (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Sep. 30, 2023
Securities AFS
Amortized Cost	$ 1,944,298	$ 2,143,333
Fair Value	1,741,221	1,804,228
Amortized Cost
Due in one year or less	1,826	5,023
Due after one year through five years	14,772	11,175
Due after five years through ten years	70,894	79,139
Due after ten years	463,257	552,360
Total Amortized Cost	550,749	647,697
Mortgage-backed securities	1,393,549	1,495,636
Amortized Cost	1,944,298	2,143,333
Fair Value
Due in one year or less	1,796	4,971
Due after one year through five years	14,211	10,292
Due after five years through ten years	63,636	66,428
Due after ten years	430,210	497,012
Total Fair Value	509,853	578,703
Mortgage-backed securities	1,231,368	1,225,525
Total debt securities AFS	1,741,221	1,804,228
Securities HTM
Amortized Cost	33,092	36,591
Gross Unrealized Gains	0	0
Gross Unrealized (Losses)	(2,856)	(5,166)
Fair Value	30,236	31,425
Held-to-maturity securities in a continuous unrealized loss position [Abstract]
LESS THAN 12 MONTHS, Fair Value	0	0
LESS THAN 12 MONTHS, Gross Unrealized (Losses)	0	0
OVER 12 MONTHS, Fair Value	30,236	31,425
OVER 12 MONTHS, Gross Unrealized (Losses)	(2,856)	(5,166)
TOTAL, Fair Value	30,236	31,425
TOTAL, Gross Unrealized (Losses)	(2,856)	(5,166)
Amortized Cost
Due after ten years	31,060	34,415
Total	31,060	34,415
Mortgage-backed securities	2,032	2,176
Total debt securities HTM	33,092	36,591
Fair Value
Due after ten years	28,392	29,571
Total	28,392	29,571
Mortgage-backed securities	1,844	1,854
Fair Value	30,236	31,425
Corporate securities
Securities AFS
Amortized Cost	25,000	25,000
Gross Unrealized Gains	0	0
Gross Unrealized (Losses)	(5,250)	(6,750)
Fair Value	19,750	18,250
Available-for-sale securities in a continuous unrealized loss position [Abstract]
Fair Value, Less than 12 months	0	0
Unrealized (Losses), Less than 12 months	0	0
Fair Value, 12 Months or Longer	19,750	18,250
Unrealized (Losses), 12 Months or Longer	(5,250)	(6,750)
Fair Value, Total	19,750	18,250
Unrealized (Losses), Total	(5,250)	(6,750)
Amortized Cost
Amortized Cost	25,000	25,000
Fair Value
Total debt securities AFS	19,750	18,250
SBA securities
Securities AFS
Amortized Cost	86,036	95,549
Gross Unrealized Gains	0	0
Gross Unrealized (Losses)	(4,101)	(10,307)
Fair Value	81,935	85,242
Available-for-sale securities in a continuous unrealized loss position [Abstract]
Fair Value, Less than 12 months	0	22,327
Unrealized (Losses), Less than 12 months	0	(1,919)
Fair Value, 12 Months or Longer	81,935	62,915
Unrealized (Losses), 12 Months or Longer	(4,101)	(8,388)
Fair Value, Total	81,935	85,242
Unrealized (Losses), Total	(4,101)	(10,307)
Amortized Cost
Amortized Cost	86,036	95,549
Fair Value
Total debt securities AFS	81,935	85,242
Obligations of states and political subdivisions
Securities AFS
Amortized Cost	501	2,368
Gross Unrealized Gains	0	0
Gross Unrealized (Losses)	(21)	(79)
Fair Value	480	2,289
Available-for-sale securities in a continuous unrealized loss position [Abstract]
Fair Value, Less than 12 months	0	0
Unrealized (Losses), Less than 12 months	0	0
Fair Value, 12 Months or Longer	280	2,289
Unrealized (Losses), 12 Months or Longer	(21)	(79)
Fair Value, Total	280	2,289
Unrealized (Losses), Total	(21)	(79)
Amortized Cost
Amortized Cost	501	2,368
Fair Value
Total debt securities AFS	480	2,289
Non-bank qualified obligations of states and political subdivisions
Securities AFS
Amortized Cost	246,233	269,396
Gross Unrealized Gains	44	0
Gross Unrealized (Losses)	(28,287)	(42,673)
Fair Value	217,990	226,723
Available-for-sale securities in a continuous unrealized loss position [Abstract]
Fair Value, Less than 12 months	0	5,010
Unrealized (Losses), Less than 12 months	0	(83)
Fair Value, 12 Months or Longer	215,956	221,714
Unrealized (Losses), 12 Months or Longer	(28,287)	(42,590)
Fair Value, Total	215,956	226,723
Unrealized (Losses), Total	(28,287)	(42,673)
Amortized Cost
Amortized Cost	246,233	269,396
Fair Value
Total debt securities AFS	217,990	226,723
Securities HTM
Amortized Cost	31,060	34,415
Gross Unrealized Gains	0	0
Gross Unrealized (Losses)	(2,668)	(4,844)
Fair Value	28,392	29,571
Held-to-maturity securities in a continuous unrealized loss position [Abstract]
LESS THAN 12 MONTHS, Fair Value	0	0
LESS THAN 12 MONTHS, Gross Unrealized (Losses)	0	0
OVER 12 MONTHS, Fair Value	28,392	29,571
OVER 12 MONTHS, Gross Unrealized (Losses)	(2,668)	(4,844)
TOTAL, Fair Value	28,392	29,571
TOTAL, Gross Unrealized (Losses)	(2,668)	(4,844)
Amortized Cost
Total debt securities HTM	31,060	34,415
Fair Value
Fair Value	28,392	29,571
Asset-backed securities
Securities AFS
Amortized Cost	192,979	255,384
Gross Unrealized Gains	337	234
Gross Unrealized (Losses)	(3,618)	(9,419)
Fair Value	189,698	246,199
Available-for-sale securities in a continuous unrealized loss position [Abstract]
Fair Value, Less than 12 months	52,101	46,528
Unrealized (Losses), Less than 12 months	(176)	(224)
Fair Value, 12 Months or Longer	88,576	115,608
Unrealized (Losses), 12 Months or Longer	(3,442)	(9,195)
Fair Value, Total	140,677	162,136
Unrealized (Losses), Total	(3,618)	(9,419)
Amortized Cost
Amortized Cost	192,979	255,384
Fair Value
Total debt securities AFS	189,698	246,199
Mortgage-backed securities
Securities AFS
Amortized Cost	1,393,549	1,495,636
Gross Unrealized Gains	84	0
Gross Unrealized (Losses)	(162,265)	(270,111)
Fair Value	1,231,368	1,225,525
Available-for-sale securities in a continuous unrealized loss position [Abstract]
Fair Value, Less than 12 months	2,377	18,311
Unrealized (Losses), Less than 12 months	(15)	(944)
Fair Value, 12 Months or Longer	1,215,781	1,207,214
Unrealized (Losses), 12 Months or Longer	(162,250)	(269,167)
Fair Value, Total	1,218,158	1,225,525
Unrealized (Losses), Total	(162,265)	(270,111)
Amortized Cost
Amortized Cost	1,393,549	1,495,636
Fair Value
Total debt securities AFS	1,231,368	1,225,525
Securities HTM
Amortized Cost	2,032	2,176
Gross Unrealized Gains	0	0
Gross Unrealized (Losses)	(188)	(322)
Fair Value	1,844	1,854
Held-to-maturity securities in a continuous unrealized loss position [Abstract]
LESS THAN 12 MONTHS, Fair Value	0	0
LESS THAN 12 MONTHS, Gross Unrealized (Losses)	0	0
OVER 12 MONTHS, Fair Value	1,844	1,854
OVER 12 MONTHS, Gross Unrealized (Losses)	(188)	(322)
TOTAL, Fair Value	1,844	1,854
TOTAL, Gross Unrealized (Losses)	(188)	(322)
Amortized Cost
Total debt securities HTM	2,032	2,176
Fair Value
Fair Value	1,844	1,854
Total debt securities AFS
Securities AFS
Amortized Cost	1,944,298	2,143,333
Gross Unrealized Gains	465	234
Gross Unrealized (Losses)	(203,542)	(339,339)
Fair Value	1,741,221	1,804,228
Available-for-sale securities in a continuous unrealized loss position [Abstract]
Fair Value, Less than 12 months	54,478	92,176
Unrealized (Losses), Less than 12 months	(191)	(3,170)
Fair Value, 12 Months or Longer	1,622,278	1,627,990
Unrealized (Losses), 12 Months or Longer	(203,351)	(336,169)
Fair Value, Total	1,676,756	1,720,165
Unrealized (Losses), Total	(203,542)	(339,339)
Amortized Cost
Amortized Cost	1,944,298	2,143,333
Fair Value
Total debt securities AFS	$ 1,741,221	$ 1,804,228