LOANS & ALLOWANCE FOR CREDIT LOSSES - ALLOWANCE FOR LOAN LOSS AND RESERVE FOR UNFUNDED LOAN COMMITMENTS (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Jun. 30, 2020
Allowance for Credit Losses - Loans
Balance, beginning of period	$ 75,807	$ 57,085	$ 57,085
Provision for Credit Losses	11,800	2,700
Charge-offs	(2,438)	(1,077)
Recoveries	446	519
Balance, end of period	132,915	59,227	75,807
Unfunded Loan Commitment Liabilities
Balance, beginning period	323	227	227
Provision for Credit Losses	700	0
Charge-offs	0	0
Recoveries	0	0
Balance, end period	6,723	227	323
Total Allowance for Credit Losses
Balance, beginning period	76,130	57,312	57,312
Provision for Credit Losses	12,500	2,700
Charge-offs	(2,438)	(1,077)
Recoveries	446	519
Balance, end period	$ 139,638	$ 59,454	$ 76,130
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member		us-gaap:AccountingStandardsUpdate201613Member
Effect of Adoption of ASC 326
Allowance for Credit Losses - Loans
Balance, beginning of period	$ 47,300
Balance, end of period			$ 47,300
Unfunded Loan Commitment Liabilities
Balance, beginning period	5,700
Balance, end period			5,700
Total Allowance for Credit Losses
Balance, beginning period	$ 53,000
Balance, end period			$ 53,000