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BUSINESS COMBINATION - Summary of Merger-Related Expenses (Details) - Luther Burbank - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024
Business Combination [Line Items]
Merger-related expenses	$ 239	$ 26,319
Severance and employee-related
Business Combination [Line Items]
Merger-related expenses	0	18,846
Legal and Professional
Business Combination [Line Items]
Merger-related expenses	103	5,573
Charitable contributions
Business Combination [Line Items]
Merger-related expenses	0	1,000
System conversion and integration
Business Combination [Line Items]
Merger-related expenses	$ 136	$ 900

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