Loans Receivable And Allowance For Credit Losses (Delinquent Loans) (Details) - USD ($) $ in Thousands	Jun. 30, 2025	Sep. 30, 2024
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	$ 778,885	$ 639,789
Year Two	566,201	1,096,101
Year Three	1,069,855	1,372,917
Year Four	1,245,856	1,529,818
Year Five	1,417,974	827,047
Prior Years	2,854,036	2,339,984
Revolving Line of Credit	105,461	118,360
Revolving Line of Credit Converted to Term Loan	8,094	6,357
Total Amortized Cost	8,046,362	7,930,373
Financial Asset, Not Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	8,022,286	7,904,743
Financial Asset, 30 to 89 Days Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	16,032	16,049
Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	8,044	9,581
One- to Four-Family Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	175,465	242,563
Year Two	238,334	652,822
Year Three	613,819	1,063,977
Year Four	999,071	1,383,986
Year Five	1,297,656	749,865
Prior Years	2,704,513	2,223,566
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	6,028,858	6,316,779
One- to Four-Family Segment [Member] | Originated [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	3,828,903	3,950,046
One- to Four-Family Segment [Member] | Originated [Member] | Financial Asset, Not Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	175,465	241,765
Year Two	237,821	326,211
Year Three	303,716	578,430
Year Four	544,376	811,455
Year Five	758,421	521,550
Prior Years	1,797,349	1,459,500
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	3,817,148	3,938,911
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	0	64
Year Three	1,110	1,074
Year Four	998	638
Year Five	149	1,666
Prior Years	7,333	5,422
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	9,590	8,864
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	0	170
Year Three	0	49
Year Four	254	0
Year Five	108	601
Prior Years	1,803	1,451
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	2,165	2,271
One- to Four-Family Segment [Member] | Correspondent Purchased [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	2,082,861	2,239,143
One- to Four-Family Segment [Member] | Correspondent Purchased [Member] | Financial Asset, Not Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	798
Year Two	513	326,377
Year Three	308,273	482,598
Year Four	452,731	571,182
Year Five	538,846	226,048
Prior Years	777,904	624,961
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	2,078,267	2,231,964
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	0
Year Two	0	0
Year Three	720	164
Year Four	335	446
Year Five	132	0
Prior Years	1,643	2,479
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	2,830	3,089
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	1,662
Year Four	377	265
Year Five	0	0
Prior Years	1,387	2,163
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	1,764	4,090
One- to Four-Family Segment [Member] | Bulk Purchased [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	117,094	127,590
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	116,800	125,982
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	116,800	125,982
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	157	69
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	157	69
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	137	1,539
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	137	1,539
Commercial Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	595,519	385,703
Year Two	319,605	436,131
Year Three	450,597	302,624
Year Four	241,816	144,010
Year Five	118,905	76,263
Prior Years	147,155	114,172
Revolving Line of Credit	30,897	44,829
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	1,904,494	1,503,732
Commercial Segment [Member] | Commercial Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	1,720,372	1,374,054
Commercial Segment [Member] | Commercial Real Estate [Member] | Financial Asset, Not Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	511,404	338,511
Year Two	291,605	403,193
Year Three	422,999	284,493
Year Four	226,049	135,932
Year Five	112,744	74,266
Prior Years	141,666	110,448
Revolving Line of Credit	8,863	23,055
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	1,715,330	1,369,898
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	147	229
Year Two	0	807
Year Three	0	0
Year Four	858	3
Year Five	0	0
Prior Years	439	1,094
Revolving Line of Credit	210	860
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	1,654	2,993
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	142	19
Year Three	217	0
Year Four	0	0
Year Five	108	647
Prior Years	2,871	497
Revolving Line of Credit	50	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	3,388	1,163
Commercial Segment [Member] | Commercial and Industrial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	184,122	129,678
Commercial Segment [Member] | Commercial and Industrial [Member] | Financial Asset, Not Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	83,968	46,736
Year Two	27,631	32,112
Year Three	27,319	17,990
Year Four	14,909	8,052
Year Five	5,988	1,350
Prior Years	2,097	2,051
Revolving Line of Credit	20,631	20,914
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	182,543	129,205
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	227
Year Two	0	0
Year Three	62	141
Year Four	0	23
Year Five	65	0
Prior Years	0	0
Revolving Line of Credit	1,039	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	1,166	391
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	227	0
Year Three	0	0
Year Four	0	0
Year Five	0	0
Prior Years	82	82
Revolving Line of Credit	104	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	413	82
Consumer Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	7,901	11,523
Year Two	8,262	7,148
Year Three	5,439	6,316
Year Four	4,969	1,822
Year Five	1,413	919
Prior Years	2,368	2,246
Revolving Line of Credit	74,564	73,531
Revolving Line of Credit Converted to Term Loan	8,094	6,357
Total Amortized Cost	113,010	109,862
Consumer Segment [Member] | Home Equity [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	103,901	100,247
Consumer Segment [Member] | Home Equity [Member] | Financial Asset, Not Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	4,443	7,331
Year Two	5,942	4,378
Year Three	3,833	4,540
Year Four	3,753	1,437
Year Five	1,180	814
Prior Years	2,242	2,133
Revolving Line of Credit	73,935	72,721
Revolving Line of Credit Converted to Term Loan	7,939	6,084
Total Amortized Cost	103,267	99,438
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	52	0
Year Three	0	35
Year Four	153	0
Year Five	0	0
Prior Years	55	0
Revolving Line of Credit	139	349
Revolving Line of Credit Converted to Term Loan	126	87
Total Amortized Cost	525	471
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	19
Year Three	0	0
Year Four	0	0
Year Five	0	0
Prior Years	6	18
Revolving Line of Credit	74	115
Revolving Line of Credit Converted to Term Loan	29	186
Total Amortized Cost	109	338
Consumer Segment [Member] | Other [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	9,109	9,615
Consumer Segment [Member] | Other [Member] | Financial Asset, Not Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	3,390	4,109
Year Two	2,208	2,728
Year Three	1,572	1,641
Year Four	1,047	327
Year Five	233	101
Prior Years	65	95
Revolving Line of Credit	416	344
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	8,931	9,345
Consumer Segment [Member] | Other [Member] | Financial Asset, 30 to 89 Days Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	59	3
Year Two	23	9
Year Three	20	100
Year Four	8	58
Year Five	0	0
Prior Years	0	0
Revolving Line of Credit	0	2
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	110	172
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	9	80
Year Two	37	14
Year Three	14	0
Year Four	8	0
Year Five	0	4
Prior Years	0	0
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	$ 68	$ 98