Loans Receivable And Allowance For Credit Losses (Classified Loans) (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Sep. 30, 2022
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	$ 927,535	$ 1,475,411
Year Two	1,435,877	1,824,711
Year Three	1,765,063	1,019,694
Year Four	967,430	445,538
Year Five	413,654	362,766
Prior Years	2,365,476	2,254,177
Revolving Line of Credit	110,724	98,282
Total Amortized Cost	7,985,759	7,480,579
One- to Four-Family Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	583,000	1,058,519
Year Two	1,113,633	1,581,839
Year Three	1,519,214	899,289
Year Four	838,743	353,241
Year Five	326,657	318,570
Prior Years	2,281,161	2,204,900
Revolving Line of Credit	0	0
Total Amortized Cost	6,662,408	6,416,358
One- to Four-Family Segment [Member] | Originated [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	4,049,961	4,038,544
One- to Four-Family Segment [Member] | Originated [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	246,776	563,460
Year Two	588,085	930,019
Year Three	895,532	624,274
Year Four	583,237	281,342
Year Five	259,986	212,037
Prior Years	1,454,283	1,406,444
Revolving Line of Credit	0	0
Total Amortized Cost	4,027,899	4,017,576
One- to Four-Family Segment [Member] | Originated [Member] | Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	292	47
Year Two	1,339	457
Year Three	791	1,111
Year Four	1,076	518
Year Five	1,139	428
Prior Years	8,507	7,641
Revolving Line of Credit	0	0
Total Amortized Cost	13,144	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	155	0
Year Three	109	278
Year Four	559	1,106
Year Five	732	256
Prior Years	7,363	8,968
Revolving Line of Credit	0	0
Total Amortized Cost	8,918	10,766
One- to Four-Family Segment [Member] | Correspondent Purchased [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	2,472,382	2,229,337
One- to Four-Family Segment [Member] | Correspondent Purchased [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	335,623	494,854
Year Two	523,658	651,363
Year Three	621,396	273,626
Year Four	253,451	69,752
Year Five	64,274	104,150
Prior Years	665,666	627,390
Revolving Line of Credit	0	0
Total Amortized Cost	2,464,068	2,221,135
One- to Four-Family Segment [Member] | Correspondent Purchased [Member] | Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	309	0
Year Two	167	0
Year Three	1,386	0
Year Four	420	355
Year Five	358	1,186
Prior Years	2,150	1,197
Revolving Line of Credit	0	0
Total Amortized Cost	4,790	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	229	0
Year Three	0	0
Year Four	0	168
Year Five	168	513
Prior Years	3,127	4,783
Revolving Line of Credit	0	0
Total Amortized Cost	3,524	5,464
One- to Four-Family Segment [Member] | Bulk Purchased [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	140,065	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	136,828	144,840
Revolving Line of Credit	0	0
Total Amortized Cost	136,828	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	3,237	3,637
Revolving Line of Credit	0	0
Total Amortized Cost	3,237	3,637
Commercial Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	336,960	406,237
Year Two	313,352	238,454
Year Three	242,718	118,069
Year Four	127,057	90,889
Year Five	85,954	42,553
Prior Years	81,686	47,053
Revolving Line of Credit	31,958	19,901
Total Amortized Cost	1,219,685	963,156
Commercial Segment [Member] | Commercial Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	1,113,100	883,166
Commercial Segment [Member] | Commercial Real Estate [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	294,232	366,794
Year Two	260,807	221,001
Year Three	229,427	111,689
Year Four	122,602	86,456
Year Five	82,804	41,322
Prior Years	80,446	46,383
Revolving Line of Credit	10,747	7,436
Total Amortized Cost	1,081,065	881,081
Commercial Segment [Member] | Commercial Real Estate [Member] | Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	2,495	565
Year Two	28,441	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	30,936	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	286	30
Revolving Line of Credit	0	0
Total Amortized Cost	1,099	1,520
Commercial Segment [Member] | Commercial and Industrial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	106,585	79,990
Commercial Segment [Member] | Commercial and Industrial [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	26,765	38,442
Year Two	24,093	17,453
Year Three	13,291	5,708
Year Four	3,788	4,212
Year Five	2,931	919
Prior Years	871	630
Revolving Line of Credit	20,275	11,413
Total Amortized Cost	92,014	78,777
Commercial Segment [Member] | Commercial and Industrial [Member] | Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	13,468	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	936	0
Total Amortized Cost	14,404	0
Commercial Segment [Member] | Commercial and Industrial [Member] | Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	0
Year Two	11	0
Year Three	0	78
Year Four	73	0
Year Five	0	73
Prior Years	83	10
Revolving Line of Credit	0	1,052
Total Amortized Cost	167	1,213
Consumer Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	7,575	10,655
Year Two	8,892	4,418
Year Three	3,131	2,336
Year Four	1,630	1,408
Year Five	1,043	1,643
Prior Years	2,629	2,224
Revolving Line of Credit	78,766	78,381
Total Amortized Cost	103,666	101,065
Consumer Segment [Member] | Home Equity [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	95,035	92,401
Consumer Segment [Member] | Home Equity [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	4,152	6,447
Year Two	5,802	2,375
Year Three	2,093	1,486
Year Four	1,202	982
Year Five	858	992
Prior Years	2,339	2,020
Revolving Line of Credit	77,968	77,448
Total Amortized Cost	94,414	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	73	0
Revolving Line of Credit	234	233
Total Amortized Cost	353	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	17	0
Prior Years	15	3
Revolving Line of Credit	236	331
Total Amortized Cost	268	352
Consumer Segment [Member] | Other [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	8,631	8,664
Consumer Segment [Member] | Other [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	3,423	4,207
Year Two	3,044	1,977
Year Three	1,038	843
Year Four	423	408
Year Five	168	651
Prior Years	202	201
Revolving Line of Credit	328	369
Total Amortized Cost	8,626	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	0	0
Year Five	0	0
Prior Years	0	0
Revolving Line of Credit	0	0
Total Amortized Cost	$ 0	$ 1