Loans Receivable And Allowance For Credit Losses (Allowance For Credit Losses) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Financing Receivable, Allowance for Credit Loss [Line Items]
Beginning Balance	$ 9,435	$ 8,558	$ 9,226	$ 8,463
Charge-offs	(375)	(12)	(423)	(68)
Recoveries	61	73	93	224
Provision for credit losses	22,075	0	22,300	0
Ending Balance	31,196	8,619	31,196	8,619
One- to Four-Family Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Beginning Balance	3,859	5,345	3,890	5,739
Charge-offs	(46)	(10)	(64)	(56)
Recoveries	3	19	3	111
Provision for credit losses	6,563	(987)	6,550	(1,427)
Ending Balance	10,379	4,367	10,379	4,367
One- to Four-Family Segment [Member] | Originated [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Beginning Balance	2,047	2,761	2,000	2,953
Charge-offs	(46)	(10)	(64)	(30)
Recoveries	3	2	3	5
Provision for credit losses	4,463	(580)	4,528	(755)
Ending Balance	6,467	2,173	6,467	2,173
One- to Four-Family Segment [Member] | Correspondent Purchased [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Beginning Balance	1,200	1,748	1,203	1,861
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Provision for credit losses	2,155	(356)	2,152	(469)
Ending Balance	3,355	1,392	3,355	1,392
One- to Four-Family Segment [Member] | Bulk Purchased [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Beginning Balance	612	836	687	925
Charge-offs	0	0	0	(26)
Recoveries	0	17	0	106
Provision for credit losses	(55)	(51)	(130)	(203)
Ending Balance	557	802	557	802
Commercial Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Beginning Balance	5,418	3,034	5,171	2,556
Charge-offs	(325)	0	(349)	0
Recoveries	54	25	81	27
Provision for credit losses	15,181	1,029	15,425	1,505
Ending Balance	20,328	4,088	20,328	4,088
Consumer Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Beginning Balance	158	179	165	168
Charge-offs	(4)	(2)	(10)	(12)
Recoveries	4	29	9	86
Provision for credit losses	331	(42)	325	(78)
Ending Balance	$ 489	$ 164	$ 489	$ 164