CAPITAL REQUIREMENTS AND RESTRICTIONS ON RETAINED EARNINGS - Tangible Common Equity Reconciliation (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Restructuring and Related Activities [Abstract]
Total stockholders' equity	$ 645,140	$ 871,884	$ 847,308	$ 843,958
LESS: Goodwill	309,505	309,505	$ 309,505
LESS: Intangible assets	25,691
Tangible common equity	309,944
Accumulated other comprehensive income (loss)	(213,080)	$ 7,599
Tangible common equity excluding AOCI	$ 523,024