SECURITIES - Schedule of Securities Available (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Sep. 30, 2021
Available For Sale
Amortized Cost	$ 2,165,719	$ 1,855,084
Fair Value	1,882,869	1,864,899
Amortized Cost
Due in one year or less	718	810
Due after one year through five years	9,921	13,026
Due after five years through ten years	89,921	50,785
Due after ten years	483,707	773,985
Total Amortized Cost	584,267	838,606
Mortgage-backed securities	1,581,452	1,016,478
Total securities AFS, at fair value	2,165,719	1,855,084
Fair Value
Due in one year or less	715	822
Due after one year through five years	9,395	13,378
Due after five years through ten years	81,819	52,357
Due after ten years	441,943	781,313
Total Fair Value	533,872	847,870
Mortgage-backed securities	1,348,997	1,017,029
Total securities AFS, at fair value	1,882,869	1,864,899
Held To Maturity
Amortized Cost	41,682	56,669
Gross Unrealized Gains	0	193
Gross Unrealized (Losses)	(3,511)	(471)
Fair Value	38,171	56,391
Held-to-maturity securities in a continuous unrealized loss position [Abstract]
LESS THAN 12 MONTHS, Fair Value	6,252	26,096
OVER 12 MONTHS, Fair Value	31,919	0
TOTAL, Fair Value	38,171	26,096
LESS THAN 12 MONTHS, Unrealized (Losses)	(621)	(471)
OVER 12 MONTHS, Unrealized (Losses)	(2,890)	0
TOTAL, Unrealized (Losses)	(3,511)	(471)
AMORTIZED COST [Abstract]
Due after ten years	39,093	52,944
Total Amortized Cost	39,093	52,944
Mortgage-backed securities	2,589	3,725
Total securities HTM, at cost	41,682	56,669
FAIR VALUE [Abstract]
Due after ten years	35,903	52,576
Total Fair Value	35,903	52,576
Mortgage-backed securities	2,268	3,815
Total securities HTM, at cost	38,171	56,391
Corporate securities
Available For Sale
Amortized Cost	25,000	25,000
Gross Unrealized Gains	0	0
Gross Unrealized (Losses)	(2,813)	0
Fair Value	22,187	25,000
Available-for-sale securities in a continuous unrealized loss position [Abstract]
Fair Value, Less than 12 months	0
Unrealized (Losses), Less than 12 months	0
Fair Value, 12 Months or Longer	22,187
Unrealized (Losses), 12 Months or Longer	(2,813)
Fair Value, Total	22,187
Unrealized (Losses), Total	(2,813)
Amortized Cost
Total securities AFS, at fair value	25,000	25,000
Fair Value
Total securities AFS, at fair value	22,187	25,000
SBA securities
Available For Sale
Amortized Cost	105,238	151,958
Gross Unrealized Gains	0	5,251
Gross Unrealized (Losses)	(7,470)	0
Fair Value	97,768	157,209
Available-for-sale securities in a continuous unrealized loss position [Abstract]
Fair Value, Less than 12 months	97,767
Unrealized (Losses), Less than 12 months	(7,470)
Fair Value, 12 Months or Longer	0
Unrealized (Losses), 12 Months or Longer	0
Fair Value, Total	97,767
Unrealized (Losses), Total	(7,470)
Amortized Cost
Total securities AFS, at fair value	105,238	151,958
Fair Value
Total securities AFS, at fair value	97,768	157,209
Obligations of states and political subdivisions
Available For Sale
Amortized Cost	2,469	2,497
Gross Unrealized Gains	0	10
Gross Unrealized (Losses)	(125)	0
Fair Value	2,344	2,507
Available-for-sale securities in a continuous unrealized loss position [Abstract]
Fair Value, Less than 12 months	2,345
Unrealized (Losses), Less than 12 months	(125)
Fair Value, 12 Months or Longer	0
Unrealized (Losses), 12 Months or Longer	0
Fair Value, Total	2,345
Unrealized (Losses), Total	(125)
Amortized Cost
Total securities AFS, at fair value	2,469	2,497
Fair Value
Total securities AFS, at fair value	2,344	2,507
Non-bank qualified obligations of states and political subdivisions
Available For Sale
Amortized Cost	290,754	266,048
Gross Unrealized Gains	0	3,347
Gross Unrealized (Losses)	(26,971)	(1,100)
Fair Value	263,783	268,295
Available-for-sale securities in a continuous unrealized loss position [Abstract]
Fair Value, Less than 12 months	195,816	101,046
Unrealized (Losses), Less than 12 months	(19,743)	(1,100)
Fair Value, 12 Months or Longer	67,967	0
Unrealized (Losses), 12 Months or Longer	(7,228)	0
Fair Value, Total	263,783	101,046
Unrealized (Losses), Total	(26,971)	(1,100)
Amortized Cost
Total securities AFS, at fair value	290,754	266,048
Fair Value
Total securities AFS, at fair value	263,783	268,295
Held To Maturity
Amortized Cost	39,093	52,944
Gross Unrealized Gains	0	103
Gross Unrealized (Losses)	(3,190)	(471)
Fair Value	35,903	52,576
Held-to-maturity securities in a continuous unrealized loss position [Abstract]
LESS THAN 12 MONTHS, Fair Value	3,984	26,096
OVER 12 MONTHS, Fair Value	31,919	0
TOTAL, Fair Value	35,903	26,096
LESS THAN 12 MONTHS, Unrealized (Losses)	(300)	(471)
OVER 12 MONTHS, Unrealized (Losses)	(2,890)	0
TOTAL, Unrealized (Losses)	(3,190)	(471)
AMORTIZED COST [Abstract]
Total securities HTM, at cost	39,093	52,944
FAIR VALUE [Abstract]
Total securities HTM, at cost	35,903	52,576
Asset-backed securities
Available For Sale
Amortized Cost	160,806	393,103
Gross Unrealized Gains	0	3,003
Gross Unrealized (Losses)	(13,016)	(1,247)
Fair Value	147,790	394,859
Available-for-sale securities in a continuous unrealized loss position [Abstract]
Fair Value, Less than 12 months	64,886	127,110
Unrealized (Losses), Less than 12 months	(1,838)	(283)
Fair Value, 12 Months or Longer	82,904	91,553
Unrealized (Losses), 12 Months or Longer	(11,178)	(964)
Fair Value, Total	147,790	218,663
Unrealized (Losses), Total	(13,016)	(1,247)
Amortized Cost
Total securities AFS, at fair value	160,806	393,103
Fair Value
Total securities AFS, at fair value	147,790	394,859
Mortgage-backed securities
Available For Sale
Amortized Cost	1,581,452	1,016,478
Gross Unrealized Gains	0	9,728
Gross Unrealized (Losses)	(232,455)	(9,177)
Fair Value	1,348,997	1,017,029
Available-for-sale securities in a continuous unrealized loss position [Abstract]
Fair Value, Less than 12 months	816,657	759,035
Unrealized (Losses), Less than 12 months	(106,583)	(7,418)
Fair Value, 12 Months or Longer	532,340	60,792
Unrealized (Losses), 12 Months or Longer	(125,872)	(1,759)
Fair Value, Total	1,348,997	819,827
Unrealized (Losses), Total	(232,455)	(9,177)
Amortized Cost
Total securities AFS, at fair value	1,581,452	1,016,478
Fair Value
Total securities AFS, at fair value	1,348,997	1,017,029
Held To Maturity
Amortized Cost	2,589	3,725
Gross Unrealized Gains	0	90
Gross Unrealized (Losses)	(321)	0
Fair Value	2,268	3,815
Held-to-maturity securities in a continuous unrealized loss position [Abstract]
LESS THAN 12 MONTHS, Fair Value	2,268
OVER 12 MONTHS, Fair Value	0
TOTAL, Fair Value	2,268
LESS THAN 12 MONTHS, Unrealized (Losses)	(321)
OVER 12 MONTHS, Unrealized (Losses)	0
TOTAL, Unrealized (Losses)	(321)
AMORTIZED COST [Abstract]
Total securities HTM, at cost	2,589	3,725
FAIR VALUE [Abstract]
Total securities HTM, at cost	2,268	3,815
Total debt securities AFS
Available For Sale
Amortized Cost	2,165,719	1,855,084
Gross Unrealized Gains	0	21,339
Gross Unrealized (Losses)	(282,850)	(11,524)
Fair Value	1,882,869	1,864,899
Available-for-sale securities in a continuous unrealized loss position [Abstract]
Fair Value, Less than 12 months	1,177,471	987,191
Unrealized (Losses), Less than 12 months	(135,759)	(8,801)
Fair Value, 12 Months or Longer	705,398	152,345
Unrealized (Losses), 12 Months or Longer	(147,091)	(2,723)
Fair Value, Total	1,882,869	1,139,536
Unrealized (Losses), Total	(282,850)	(11,524)
Amortized Cost
Total securities AFS, at fair value	2,165,719	1,855,084
Fair Value
Total securities AFS, at fair value	$ 1,882,869	$ 1,864,899