Loans Receivable And Allowance For Credit Losses (Classified Loans) (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Sep. 30, 2022
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	$ 728,525	$ 1,475,411
Year Two	1,476,279	1,824,711
Year Three	1,796,984	1,019,694
Year Four	988,342	445,538
Year Five	425,069	362,766
Prior Years	2,454,493	2,254,177
Revolving Line of Credit	108,764	98,282
Total Amortized Cost	7,978,456	7,480,579
One- to Four-Family Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	475,437	1,058,519
Year Two	1,111,488	1,581,839
Year Three	1,548,054	899,289
Year Four	860,768	353,241
Year Five	336,657	318,570
Prior Years	2,366,722	2,204,900
Revolving Line of Credit	0	0
Total Amortized Cost	6,699,126	6,416,358
One- to Four-Family Segment [Member] | Originated [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	4,056,123	4,038,544
One- to Four-Family Segment [Member] | Originated [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	166,083	563,460
Year Two	578,258	930,019
Year Three	912,340	624,274
Year Four	597,495	281,342
Year Five	267,725	212,037
Prior Years	1,511,800	1,406,444
Revolving Line of Credit	0	0
Total Amortized Cost	4,033,701	4,017,576
One- to Four-Family Segment [Member] | Originated [Member] | Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	184	47
Year Two	1,192	457
Year Three	760	1,111
Year Four	1,365	518
Year Five	1,274	428
Prior Years	9,070	7,641
Revolving Line of Credit	0	0
Total Amortized Cost	13,845	10,202
One- to Four-Family Segment [Member] | Originated [Member] | Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	158
Year Two	187	0
Year Three	110	278
Year Four	277	1,106
Year Five	734	256
Prior Years	7,269	8,968
Revolving Line of Credit	0	0
Total Amortized Cost	8,577	10,766
One- to Four-Family Segment [Member] | Correspondent Purchased [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	2,499,971	2,229,337
One- to Four-Family Segment [Member] | Correspondent Purchased [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	309,170	494,854
Year Two	531,455	651,363
Year Three	633,831	273,626
Year Four	261,631	69,752
Year Five	66,403	104,150
Prior Years	690,477	627,390
Revolving Line of Credit	0	0
Total Amortized Cost	2,492,967	2,221,135
One- to Four-Family Segment [Member] | Correspondent Purchased [Member] | Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	0
Year Two	396	0
Year Three	1,013	0
Year Four	0	355
Year Five	353	1,186
Prior Years	1,761	1,197
Revolving Line of Credit	0	0
Total Amortized Cost	3,523	2,738
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	0
Year Four	0	168
Year Five	168	513
Prior Years	3,313	4,783
Revolving Line of Credit	0	0
Total Amortized Cost	3,481	5,464
One- to Four-Family Segment [Member] | Bulk Purchased [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	143,032	148,477
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	139,489	144,840
Revolving Line of Credit	0	0
Total Amortized Cost	139,489	144,840
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	3,543	3,637
Revolving Line of Credit	0	0
Total Amortized Cost	3,543	3,637
Commercial Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	248,158	406,237
Year Two	355,269	238,454
Year Three	245,467	118,069
Year Four	125,674	90,889
Year Five	87,283	42,553
Prior Years	84,724	47,053
Revolving Line of Credit	31,368	19,901
Total Amortized Cost	1,177,943	963,156
Commercial Segment [Member] | Commercial Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	1,087,756	883,166
Commercial Segment [Member] | Commercial Real Estate [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	228,869	366,794
Year Two	301,638	221,001
Year Three	231,200	111,689
Year Four	120,670	86,456
Year Five	83,873	41,322
Prior Years	83,290	46,383
Revolving Line of Credit	8,676	7,436
Total Amortized Cost	1,058,216	881,081
Commercial Segment [Member] | Commercial Real Estate [Member] | Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	565
Year Two	28,439	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	28,439	565
Commercial Segment [Member] | Commercial Real Estate [Member] | Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	436
Year Two	0	0
Year Three	0	594
Year Four	594	221
Year Five	219	239
Prior Years	288	30
Revolving Line of Credit	0	0
Total Amortized Cost	1,101	1,520
Commercial Segment [Member] | Commercial and Industrial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	90,187	79,990
Commercial Segment [Member] | Commercial and Industrial [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	19,289	38,442
Year Two	25,176	17,453
Year Three	14,267	5,708
Year Four	4,337	4,212
Year Five	3,191	919
Prior Years	1,063	630
Revolving Line of Credit	22,082	11,413
Total Amortized Cost	89,405	78,777
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	16	0
Year Three	0	78
Year Four	73	0
Year Five	0	73
Prior Years	83	10
Revolving Line of Credit	610	1,052
Total Amortized Cost	782	1,213
Consumer Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	4,930	10,655
Year Two	9,522	4,418
Year Three	3,463	2,336
Year Four	1,900	1,408
Year Five	1,129	1,643
Prior Years	3,047	2,224
Revolving Line of Credit	77,396	78,381
Total Amortized Cost	101,387	101,065
Consumer Segment [Member] | Home Equity [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	92,722	92,401
Consumer Segment [Member] | Home Equity [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	2,548	6,447
Year Two	5,997	2,375
Year Three	2,162	1,486
Year Four	1,342	982
Year Five	890	992
Prior Years	2,643	2,020
Revolving Line of Credit	76,618	77,448
Total Amortized Cost	92,200	91,750
Consumer Segment [Member] | Home Equity [Member] | Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	0
Year Two	46	66
Year Three	0	0
Year Four	0	0
Year Five	0	0
Prior Years	0	0
Revolving Line of Credit	245	233
Total Amortized Cost	291	299
Consumer Segment [Member] | Home Equity [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	18
Year Five	18	0
Prior Years	15	3
Revolving Line of Credit	198	331
Total Amortized Cost	231	352
Consumer Segment [Member] | Other [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	8,665	8,664
Consumer Segment [Member] | Other [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	2,382	4,207
Year Two	3,479	1,977
Year Three	1,301	843
Year Four	549	408
Year Five	221	651
Prior Years	389	201
Revolving Line of Credit	333	369
Total Amortized Cost	8,654	8,656
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	7
Year Four	5	0
Year Five	0	0
Prior Years	0	0
Revolving Line of Credit	0	0
Total Amortized Cost	5	7
Consumer Segment [Member] | Other [Member] | Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	1
Year Two	0	0
Year Three	0	0
Year Four	4	0
Year Five	0	0
Prior Years	0	0
Revolving Line of Credit	2	0
Total Amortized Cost	$ 6	$ 1