Loans Receivable And Allowance For Credit Losses (Delinquent Loans) (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Sep. 30, 2023
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	$ 508,647	$ 1,124,730
Year Two	1,087,706	1,450,679
Year Three	1,404,393	1,709,273
Year Four	1,558,403	904,106
Year Five	846,098	403,494
Prior Years	2,433,509	2,285,008
Revolving Line of Credit	113,442	110,969
Revolving Line of Credit Converted to Term Loan	6,699	6,449
Total Amortized Cost	7,958,897	7,994,708
Financial Asset, Not Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	7,933,806	7,969,425
Financial Asset, 30 to 89 Days Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	16,452	16,347
Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	8,639	8,936
One- to Four-Family Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	172,597	665,253
Year Two	661,069	1,117,986
Year Three	1,079,102	1,485,849
Year Four	1,408,455	817,322
Year Five	766,531	317,676
Prior Years	2,302,415	2,202,364
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	6,390,169	6,606,450
One- to Four-Family Segment [Member] | Originated [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	3,970,963	4,033,028
One- to Four-Family Segment [Member] | Originated [Member] | Financial Asset, Not Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	171,792	318,211
Year Two	328,747	598,283
Year Three	587,828	875,563
Year Four	826,342	567,975
Year Five	534,663	253,546
Prior Years	1,512,418	1,407,090
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	3,961,790	4,020,668
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	358
Year Two	170	898
Year Three	499	644
Year Four	636	1,437
Year Five	783	820
Prior Years	5,040	5,960
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	7,128	10,117
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	292
Year Two	0	155
Year Three	28	0
Year Four	0	0
Year Five	0	209
Prior Years	2,017	1,587
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	2,045	2,243
One- to Four-Family Segment [Member] | Correspondent Purchased [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	2,289,664	2,435,750
One- to Four-Family Segment [Member] | Correspondent Purchased [Member] | Financial Asset, Not Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	805	346,084
Year Two	331,608	518,650
Year Three	489,165	608,573
Year Four	581,028	247,346
Year Five	230,327	62,652
Prior Years	647,470	643,739
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	2,280,403	2,427,044
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	308
Year Two	544	0
Year Three	164	1,069
Year Four	449	564
Year Five	0	449
Prior Years	4,181	2,862
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	5,338	5,252
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	1,418	0
Year Four	0	0
Year Five	758	0
Prior Years	1,747	3,454
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	3,923	3,454
One- to Four-Family Segment [Member] | Bulk Purchased [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	129,542	137,672
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	127,990	136,577
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	127,990	136,577
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	277	153
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	277	153
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	1,275	942
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	1,275	942
Commercial Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	326,682	449,216
Year Two	418,564	324,330
Year Three	318,632	220,682
Year Four	148,003	85,373
Year Five	78,567	84,939
Prior Years	128,628	80,255
Revolving Line of Credit	41,027	38,251
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	1,460,103	1,283,046
Commercial Segment [Member] | Commercial Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	1,328,245	1,170,116
Commercial Segment [Member] | Commercial Real Estate [Member] | Financial Asset, Not Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	286,592	404,867
Year Two	379,498	301,164
Year Three	299,974	208,942
Year Four	139,033	81,478
Year Five	76,159	82,027
Prior Years	124,529	79,188
Revolving Line of Credit	18,866	10,448
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	1,324,651	1,168,114
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	36
Year Two	786	0
Year Three	0	0
Year Four	151	0
Year Five	54	0
Prior Years	1,296	0
Revolving Line of Credit	229	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	2,516	36
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	916
Year Two	20	0
Year Three	0	0
Year Four	0	594
Year Five	594	219
Prior Years	464	237
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	1,078	1,966
Commercial Segment [Member] | Commercial and Industrial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	131,858	112,930
Commercial Segment [Member] | Commercial and Industrial [Member] | Financial Asset, Not Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	40,090	43,397
Year Two	38,260	23,166
Year Three	18,514	11,740
Year Four	8,795	3,228
Year Five	1,760	2,690
Prior Years	2,257	748
Revolving Line of Credit	21,834	27,684
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	131,510	112,653
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	144	0
Year Four	24	0
Year Five	0	2
Prior Years	0	0
Revolving Line of Credit	98	57
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	266	59
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	73
Year Five	0	1
Prior Years	82	82
Revolving Line of Credit	0	62
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	82	218
Consumer Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	9,368	10,261
Year Two	8,073	8,363
Year Three	6,659	2,742
Year Four	1,945	1,411
Year Five	1,000	879
Prior Years	2,466	2,389
Revolving Line of Credit	72,415	72,718
Revolving Line of Credit Converted to Term Loan	6,699	6,449
Total Amortized Cost	108,625	105,212
Consumer Segment [Member] | Home Equity [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	98,988	95,955
Consumer Segment [Member] | Home Equity [Member] | Financial Asset, Not Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	5,894	5,428
Year Two	4,828	5,631
Year Three	4,670	1,955
Year Four	1,512	990
Year Five	814	746
Prior Years	2,304	2,195
Revolving Line of Credit	71,657	71,986
Revolving Line of Credit Converted to Term Loan	6,397	6,312
Total Amortized Cost	98,076	95,243
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	73
Year Two	20	39
Year Three	45	0
Year Four	0	79
Year Five	0	0
Prior Years	30	50
Revolving Line of Credit	321	239
Revolving Line of Credit Converted to Term Loan	302	125
Total Amortized Cost	718	605
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	0
Year Three	0	0
Year Four	0	0
Year Five	54	0
Prior Years	3	15
Revolving Line of Credit	137	81
Revolving Line of Credit Converted to Term Loan	0	11
Total Amortized Cost	194	107
Consumer Segment [Member] | Other [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	9,637	9,257
Consumer Segment [Member] | Other [Member] | Financial Asset, Not Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	3,372	4,737
Year Two	3,171	2,613
Year Three	1,886	765
Year Four	433	338
Year Five	124	132
Prior Years	107	129
Revolving Line of Credit	293	412
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	9,386	9,126
Consumer Segment [Member] | Other [Member] | Financial Asset, 30 to 89 Days Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	102	17
Year Two	23	80
Year Three	56	22
Year Four	0	4
Year Five	4	1
Prior Years	22	0
Revolving Line of Credit	2	0
Revolving Line of Credit Converted to Term Loan	0	1
Total Amortized Cost	209	125
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	6
Year Two	31	0
Year Three	2	0
Year Four	0	0
Year Five	4	0
Prior Years	0	0
Revolving Line of Credit	5	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	$ 42	$ 6