CAPITAL REQUIREMENTS AND RESTRICTIONS ON RETAINED EARNINGS - Financial Measures of Capital (Details)	Sep. 30, 2022	Sep. 30, 2021
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier 1 (core) capital (to adjusted total assets), ratio	8.10%	7.67%
Tier 1 (core) capital (to adjusted total assets), minimum requirement for capital adequacy purposes, ratio	4.00%	4.00%
Tier 1 (core) capital (to adjusted total assets), minimum requirement to be well capitalized under prompt corrective action provisions, ratio	5.00%	5.00%
Common equity Tier 1 (to risk-weighted assets), actual ratio	12.07%	12.12%
Common equity Tier 1 (to risk-weighted assets), minimum requirement for capital adequacy purposes, ratio	4.50%	4.50%
Common equity Tier 1 (to risk-weighted assets), minimum requirement to be well capitalized under prompt corrective action provisions, ratio	6.50%	6.50%
Tier 1 (core) capital ( to risk weighted assets), ratio	0.1239	0.1246
Tier 1 (core) capital (to risk-weighted assets), minimum requirement for capital adequacy purposes, ratio	0.0600	0.0600
Tier 1 (core) capital (to risk-weighted assets), minimum requirement to be well capitalized under prompt corrective action provisions, ratio	0.0800	0.0800
Total qualifying capital (to risk-weighted assets), ratio	13.88%	15.45%
Total qualifying capital (to risk-weighted assets), minimum requirement for capital adequacy purposes, ratio	8.00%	8.00%
Total qualifying capital (to risk-weighted assets), minimum requirement to be well capitalized under prompt corrective action provisions, ratio	10.00%	10.00%
MetaBank
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier 1 (core) capital (to adjusted total assets), ratio	8.19%	8.69%
Common equity Tier 1 (to risk-weighted assets), actual ratio	12.55%	14.11%
Tier 1 (core) capital ( to risk weighted assets), ratio	0.1255	0.1413
Total qualifying capital (to risk-weighted assets), ratio	13.57%	15.38%