Loans Receivable And Allowance For Credit Losses (Delinquent Loans) (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Sep. 30, 2021
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	$ 995,159	$ 1,953,147
Year Two	1,925,187	1,204,963
Year Three	1,058,802	520,852
Year Four	457,001	455,353
Year Five	375,096	485,640
Prior Years	2,347,182	2,388,212
Revolving Line of Credit	94,052	92,798
Total Amortized Cost	7,252,479	7,100,965
Financial Asset, Not Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	7,232,781	7,081,450
Financial Asset, 30 to 89 Days Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	11,243	7,861
Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	8,455	11,654
One- to Four-Family Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	742,687	1,590,219
Year Two	1,608,062	1,041,012
Year Three	920,678	416,106
Year Four	362,920	388,651
Year Five	328,547	444,471
Prior Years	2,292,956	2,300,036
Revolving Line of Credit	0	0
Total Amortized Cost	6,255,850	6,180,495
One- to Four-Family Segment [Member] | Originated [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	4,007,912	3,979,536
One- to Four-Family Segment [Member] | Originated [Member] | Financial Asset, Not Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	431,123	958,482
Year Two	940,401	706,970
Year Three	640,648	327,408
Year Four	289,459	251,524
Year Five	219,361	281,341
Prior Years	1,478,318	1,445,992
Revolving Line of Credit	0	0
Total Amortized Cost	3,999,310	3,971,717
One- to Four-Family Segment [Member] | Originated [Member] | Financial Asset, 30 to 89 Days Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	0
Year Two	112	0
Year Three	424	0
Year Four	610	51
Year Five	302	0
Prior Years	4,573	4,091
Revolving Line of Credit	0	0
Total Amortized Cost	6,021	4,142
One- to Four-Family Segment [Member] | Originated [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	0
Year Two	115	0
Year Three	0	116
Year Four	290	0
Year Five	108	192
Prior Years	2,068	3,369
Revolving Line of Credit	0	0
Total Amortized Cost	2,581	3,677
One- to Four-Family Segment [Member] | Correspondent Purchased [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	2,095,922	2,026,592
One- to Four-Family Segment [Member] | Correspondent Purchased [Member] | Financial Asset, Not Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	311,564	630,977
Year Two	666,687	334,042
Year Three	279,606	88,413
Year Four	72,393	136,572
Year Five	107,281	162,017
Prior Years	652,183	668,685
Revolving Line of Credit	0	0
Total Amortized Cost	2,089,714	2,020,706
One- to Four-Family Segment [Member] | Correspondent Purchased [Member] | Financial Asset, 30 to 89 Days Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	760
Year Two	747	0
Year Three	0	0
Year Four	0	0
Year Five	979	921
Prior Years	1,787	948
Revolving Line of Credit	0	0
Total Amortized Cost	3,513	2,629
One- to Four-Family Segment [Member] | Correspondent Purchased [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	0
Year Two	0	0
Year Three	0	169
Year Four	168	504
Year Five	516	0
Prior Years	2,011	2,584
Revolving Line of Credit	0	0
Total Amortized Cost	2,695	3,257
One- to Four-Family Segment [Member] | Bulk Purchased [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	152,016	174,367
One- to Four-Family Segment [Member] | Bulk Purchased [Member] | Financial Asset, Not Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	0
Year Two	0	0
Year Three	0	0
Year Four	0	0
Year Five	0	0
Prior Years	149,444	170,809
Revolving Line of Credit	0	0
Total Amortized Cost	149,444	170,809
One- to Four-Family Segment [Member] | Bulk Purchased [Member] | Financial Asset, 30 to 89 Days Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	0
Year Two	0	0
Year Three	0	0
Year Four	0	0
Year Five	0	0
Prior Years	755	555
Revolving Line of Credit	0	0
Total Amortized Cost	755	555
One- to Four-Family Segment [Member] | Bulk Purchased [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	0
Year Two	0	0
Year Three	0	0
Year Four	0	0
Year Five	0	0
Prior Years	1,817	3,003
Revolving Line of Credit	0	0
Total Amortized Cost	1,817	3,003
Commercial Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	245,425	356,142
Year Two	312,368	160,039
Year Three	135,497	102,185
Year Four	92,445	64,182
Year Five	44,767	40,165
Prior Years	51,778	85,589
Revolving Line of Credit	18,648	17,705
Total Amortized Cost	900,928	826,007
Commercial Segment [Member] | Commercial Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	829,968	759,629
Commercial Segment [Member] | Commercial Real Estate [Member] | Financial Asset, Not Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	218,782	323,491
Year Two	293,349	149,244
Year Three	127,863	94,972
Year Four	87,546	61,651
Year Five	43,213	38,962
Prior Years	50,515	84,957
Revolving Line of Credit	6,950	5,231
Total Amortized Cost	828,218	758,508
Commercial Segment [Member] | Commercial Real Estate [Member] | Financial Asset, 30 to 89 Days Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	0
Year Two	0	0
Year Three	72	0
Year Four	0	0
Year Five	109	0
Prior Years	494	37
Revolving Line of Credit	0	0
Total Amortized Cost	675	37
Commercial Segment [Member] | Commercial Real Estate [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	0
Year Two	0	627
Year Three	594	225
Year Four	222	232
Year Five	230	0
Prior Years	29	0
Revolving Line of Credit	0	0
Total Amortized Cost	1,075	1,084
Commercial Segment [Member] | Commercial and Industrial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	70,960	66,378
Commercial Segment [Member] | Commercial and Industrial [Member] | Financial Asset, Not Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	26,643	32,651
Year Two	19,019	10,168
Year Three	6,968	6,988
Year Four	4,672	2,212
Year Five	1,116	1,155
Prior Years	708	595
Revolving Line of Credit	11,698	12,474
Total Amortized Cost	70,824	66,243
Commercial Segment [Member] | Commercial and Industrial [Member] | Financial Asset, 30 to 89 Days Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	0
Year Two	0	0
Year Three	0	0
Year Four	5	0
Year Five	18	0
Prior Years	0	0
Revolving Line of Credit	0	0
Total Amortized Cost	23	0
Commercial Segment [Member] | Commercial and Industrial [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	0
Year Two	0	0
Year Three	0	0
Year Four	0	87
Year Five	81	48
Prior Years	32	0
Revolving Line of Credit	0	0
Total Amortized Cost	113	135
Consumer Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	7,047	6,786
Year Two	4,757	3,912
Year Three	2,627	2,561
Year Four	1,636	2,520
Year Five	1,782	1,004
Prior Years	2,448	2,587
Revolving Line of Credit	75,404	75,093
Total Amortized Cost	95,701	94,463
Consumer Segment [Member] | Home Equity [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	87,414	86,385
Consumer Segment [Member] | Home Equity [Member] | Financial Asset, Not Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	3,832	3,295
Year Two	2,541	2,218
Year Three	1,613	1,465
Year Four	1,060	1,575
Year Five	1,085	536
Prior Years	2,162	2,357
Revolving Line of Credit	74,717	73,958
Total Amortized Cost	87,010	85,404
Consumer Segment [Member] | Home Equity [Member] | Financial Asset, 30 to 89 Days Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	0
Year Two	0	0
Year Three	0	0
Year Four	0	0
Year Five	0	0
Prior Years	66	121
Revolving Line of Credit	164	375
Total Amortized Cost	230	496
Consumer Segment [Member] | Home Equity [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	0
Year Two	0	60
Year Three	0	0
Year Four	0	0
Year Five	0	0
Prior Years	8	4
Revolving Line of Credit	166	421
Total Amortized Cost	174	485
Consumer Segment [Member] | Other [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	8,287	8,078
Consumer Segment [Member] | Other [Member] | Financial Asset, Not Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	3,209	3,491
Year Two	2,203	1,631
Year Three	1,014	1,088
Year Four	571	944
Year Five	697	465
Prior Years	212	105
Revolving Line of Credit	355	339
Total Amortized Cost	8,261	8,063
Consumer Segment [Member] | Other [Member] | Financial Asset, 30 to 89 Days Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	6	0
Year Two	13	0
Year Three	0	2
Year Four	5	0
Year Five	0	0
Prior Years	0	0
Revolving Line of Credit	2	0
Total Amortized Cost	26	2
Consumer Segment [Member] | Other [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	0
Year Two	0	3
Year Three	0	6
Year Four	0	1
Year Five	0	3
Prior Years	0	0
Revolving Line of Credit	0	0
Total Amortized Cost	$ 0	$ 13