Consolidated Statements Of Income - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
INTEREST AND DIVIDEND INCOME:
Loans receivable	$ 270,494	$ 284,229	$ 260,198
Mortgage-backed securities ("MBS")	23,009	25,730	22,619
FHLB stock	5,827	7,823	10,962
Investment securities	4,467	6,366	4,670
Cash and cash equivalents	1,181	5,806	23,443
Total interest and dividend income	304,978	329,954	321,892
INTEREST EXPENSE:
Deposits	67,598	66,201	52,625
Borrowings	48,045	57,363	70,494
Total interest expense	115,643	123,564	123,119
NET INTEREST INCOME	189,335	206,390	198,773
PROVISION FOR CREDIT LOSSES	22,300	750	0
NET INTEREST INCOME AFTER PROVISION FOR CREDIT LOSSES	167,035	205,640	198,773
NON-INTEREST INCOME:
Revenue from contracts with customers	14,800	16,600	$ 15,636
Deposit service fees, type of revenue			us-gaap:DepositAccountMember
Insurance Commissions			$ 2,469
Other non-interest income	5,827	6,397	3,930
Total non-interest income	19,599	21,958	22,035
NON-INTEREST EXPENSE:
Salaries and employee benefits	52,996	53,145	46,563
Information technology and related expense	16,974	17,615	13,999
Occupancy, net	13,870	13,032	11,455
Regulatory and outside services	5,762	5,813	5,709
Advertising and promotional	4,889	5,244	5,034
Deposit and loan transaction costs	2,890	2,478	5,621
Office supplies and related expense	2,195	2,439	1,888
Federal insurance premium	914	1,172	3,277
Other non-interest expense	5,514	6,006	3,356
Total non-interest expense	106,004	106,944	96,902
INCOME BEFORE INCOME TAX EXPENSE	80,630	120,654	123,906
INCOME TAX EXPENSE	16,090	26,411	24,979
NET INCOME	$ 64,540	$ 94,243	$ 98,927
Basic earnings per share ("EPS")	$ 0.47	$ 0.68	$ 0.73
Diluted EPS	$ 0.47	$ 0.68	$ 0.73
Deposit service fees [Member]
NON-INTEREST INCOME:
Revenue from contracts with customers	$ 11,285	$ 12,740
Insurance commissions [Member]
NON-INTEREST INCOME:
Revenue from contracts with customers	$ 2,487	$ 2,821