Loans Receivable And Allowance For Credit Losses (Allowance For Credit Losses) (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Financing Receivable, Allowance for Credit Loss [Line Items]
Beginning Balance	$ 9,226	$ 8,463	$ 8,398
Charge-offs	(443)	(262)	(302)
Recoveries	444	275	367
Provision for credit losses	22,300	750	0
Ending Balance	31,527	9,226	8,463
One- to Four-Family Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Beginning Balance	3,890	5,739	6,095
Charge-offs	(64)	(101)	(264)
Recoveries	306	128	340
Provision for credit losses	5,111	(1,876)	(432)
Ending Balance	9,243	3,890	5,739
One- to Four-Family Segment [Member] | Originated [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Beginning Balance	2,000	2,953	3,173
Charge-offs	(64)	(75)	(136)
Recoveries	41	22	144
Provision for credit losses	4,108	(900)	(228)
Ending Balance	6,085	2,000	2,953
One- to Four-Family Segment [Member] | Correspondent Purchased [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Beginning Balance	1,203	1,861	1,922
Charge-offs	0	0	(128)
Recoveries	0	0	0
Provision for credit losses	1,488	(658)	67
Ending Balance	2,691	1,203	1,861
One- to Four-Family Segment [Member] | Bulk Purchased [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Beginning Balance	687	925	1,000
Charge-offs	0	(26)	0
Recoveries	265	106	196
Provision for credit losses	(485)	(318)	(271)
Ending Balance	467	687	925
Commercial Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Beginning Balance	5,171	2,556	2,112
Charge-offs	(349)	(124)	0
Recoveries	110	49	0
Provision for credit losses	16,868	2,690	444
Ending Balance	21,800	5,171	2,556
Consumer Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Beginning Balance	165	168	191
Charge-offs	(30)	(37)	(38)
Recoveries	28	98	27
Provision for credit losses	321	(64)	(12)
Ending Balance	$ 484	$ 165	$ 168