Loans Receivable And Allowance For Credit Losses (Classified 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
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] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	431,090	958,080
Year Two	940,258	705,561
Year Three	639,580	326,156
Year Four	288,707	250,846
Year Five	218,917	281,104
Prior Years	1,467,749	1,434,455
Revolving Line of Credit	0	0
Total Amortized Cost	3,986,301	3,956,202
One- to Four-Family Segment [Member] | Originated [Member] | Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	33	402
Year Two	255	443
Year Three	1,213	501
Year Four	621	678
Year Five	598	237
Prior Years	8,261	7,805
Revolving Line of Credit	0	0
Total Amortized Cost	10,981	10,066
One- to Four-Family Segment [Member] | Originated [Member] | Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	0
Year Two	115	966
Year Three	279	867
Year Four	1,031	51
Year Five	256	192
Prior Years	8,949	11,192
Revolving Line of Credit	0	0
Total Amortized Cost	10,630	13,268
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] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	311,564	630,977
Year Two	667,434	334,042
Year Three	279,606	88,057
Year Four	72,042	136,572
Year Five	107,281	162,938
Prior Years	650,328	664,530
Revolving Line of Credit	0	0
Total Amortized Cost	2,088,255	2,017,116
One- to Four-Family Segment [Member] | Correspondent Purchased [Member] | Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	760
Year Two	0	0
Year Three	0	356
Year Four	351	0
Year Five	979	0
Prior Years	1,840	3,160
Revolving Line of Credit	0	0
Total Amortized Cost	3,170	4,276
One- to Four-Family Segment [Member] | Correspondent Purchased [Member] | Substandard [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	3,813	4,527
Revolving Line of Credit	0	0
Total Amortized Cost	4,497	5,200
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] | Pass [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	147,961	169,519
Revolving Line of Credit	0	0
Total Amortized Cost	147,961	169,519
One- to Four-Family Segment [Member] | Bulk Purchased [Member] | Special Mention [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	0	0
Revolving Line of Credit	0	0
Total Amortized Cost	0	0
One- to Four-Family Segment [Member] | Bulk Purchased [Member] | Substandard [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	4,055	4,848
Revolving Line of Credit	0	0
Total Amortized Cost	4,055	4,848
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] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	218,340	272,329
Year Two	246,384	149,244
Year Three	127,935	94,972
Year Four	87,546	61,214
Year Five	43,322	38,962
Prior Years	51,008	35,591
Revolving Line of Credit	6,950	5,231
Total Amortized Cost	781,485	657,543
Commercial Segment [Member] | Commercial Real Estate [Member] | Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	50,352
Year Two	46,366	0
Year Three	0	0
Year Four	0	0
Year Five	0	0
Prior Years	0	49,369
Revolving Line of Credit	0	0
Total Amortized Cost	46,366	99,721
Commercial Segment [Member] | Commercial Real Estate [Member] | Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	442	810
Year Two	599	627
Year Three	594	225
Year Four	222	669
Year Five	230	0
Prior Years	30	34
Revolving Line of Credit	0	0
Total Amortized Cost	2,117	2,365
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] | Pass [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	4,677	2,213
Year Five	1,134	1,155
Prior Years	708	595
Revolving Line of Credit	10,846	11,709
Total Amortized Cost	69,995	65,479
Commercial Segment [Member] | Commercial and Industrial [Member] | Special Mention [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	0	0
Revolving Line of Credit	0	0
Total Amortized Cost	0	0
Commercial Segment [Member] | Commercial and Industrial [Member] | Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	0
Year Two	0	0
Year Three	0	0
Year Four	0	86
Year Five	81	48
Prior Years	32	0
Revolving Line of Credit	852	765
Total Amortized Cost	965	899
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] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	3,832	3,295
Year Two	2,541	2,218
Year Three	1,613	1,428
Year Four	1,041	1,563
Year Five	1,085	536
Prior Years	2,224	2,473
Revolving Line of Credit	74,406	74,036
Total Amortized Cost	86,742	85,549
Consumer Segment [Member] | Home Equity [Member] | Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	0
Year Two	0	0
Year Three	0	37
Year Four	0	12
Year Five	0	0
Prior Years	0	0
Revolving Line of Credit	288	82
Total Amortized Cost	288	131
Consumer Segment [Member] | Home Equity [Member] | Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	0
Year Two	0	60
Year Three	0	0
Year Four	19	0
Year Five	0	0
Prior Years	12	9
Revolving Line of Credit	353	636
Total Amortized Cost	384	705
Consumer Segment [Member] | Other [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	8,287	8,078
Consumer Segment [Member] | Other [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	3,215	3,491
Year Two	2,216	1,631
Year Three	1,014	1,086
Year Four	576	944
Year Five	697	465
Prior Years	212	105
Revolving Line of Credit	357	339
Total Amortized Cost	8,287	8,061
Consumer Segment [Member] | Other [Member] | Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	0
Year Two	0	0
Year Three	0	4
Year Four	0	0
Year Five	0	0
Prior Years	0	0
Revolving Line of Credit	0	0
Total Amortized Cost	0	4
Consumer Segment [Member] | Other [Member] | Substandard [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