Loans Receivable And Allowance For Credit Losses (Classified 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
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] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	171,792	318,569
Year Two	328,132	597,298
Year Three	585,775	874,518
Year Four	824,314	568,081
Year Five	533,544	251,773
Prior Years	1,499,900	1,398,616
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	3,943,457	4,008,855
One- to Four-Family Segment [Member] | Originated [Member] | Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	0
Year Two	295	1,883
Year Three	2,552	1,468
Year Four	2,446	767
Year Five	1,345	1,863
Prior Years	9,781	8,067
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	16,419	14,048
One- to Four-Family Segment [Member] | Originated [Member] | Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	292
Year Two	490	155
Year Three	28	221
Year Four	218	564
Year Five	557	939
Prior Years	9,794	7,954
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	11,087	10,125
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] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	805	346,084
Year Two	331,495	517,976
Year Three	488,423	607,968
Year Four	580,549	246,926
Year Five	229,921	62,744
Prior Years	647,375	643,520
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	2,278,568	2,425,218
One- to Four-Family Segment [Member] | Correspondent Purchased [Member] | Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	308
Year Two	657	674
Year Three	906	1,674
Year Four	663	420
Year Five	406	357
Prior Years	1,281	1,133
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	3,913	4,566
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	1,418	0
Year Four	265	564
Year Five	758	0
Prior Years	4,742	5,402
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	7,183	5,966
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] | 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	126,268	134,464
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	126,268	134,464
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
Revolving Line of Credit Converted to Term Loan	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	3,274	3,208
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	3,274	3,208
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] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	281,804	403,269
Year Two	374,479	301,164
Year Three	299,974	208,942
Year Four	139,184	81,478
Year Five	76,159	82,027
Prior Years	124,529	79,170
Revolving Line of Credit	19,045	10,448
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	1,315,174	1,166,498
Commercial Segment [Member] | Commercial Real Estate [Member] | Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	4,646	2,483
Year Two	5,020	0
Year Three	0	0
Year Four	0	0
Year Five	54	0
Prior Years	1,154	0
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	10,874	2,483
Commercial Segment [Member] | Commercial Real Estate [Member] | Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	142	67
Year Two	805	0
Year Three	0	0
Year Four	0	594
Year Five	594	219
Prior Years	606	255
Revolving Line of Credit	50	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	2,197	1,135
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] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	39,635	30,206
Year Two	26,210	23,166
Year Three	18,658	11,740
Year Four	8,819	3,228
Year Five	1,760	2,693
Prior Years	2,257	748
Revolving Line of Credit	21,901	27,104
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	119,240	98,885
Commercial Segment [Member] | Commercial and Industrial [Member] | Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	228	13,191
Year Two	12,050	0
Year Three	0	0
Year Four	0	0
Year Five	0	0
Prior Years	0	0
Revolving Line of Credit	0	699
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	12,278	13,890
Commercial Segment [Member] | Commercial and Industrial [Member] | Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	227	0
Year Two	0	0
Year Three	0	0
Year Four	0	73
Year Five	0	0
Prior Years	82	82
Revolving Line of Credit	31	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	340	155
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] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	5,894	5,501
Year Two	4,848	5,624
Year Three	4,715	1,955
Year Four	1,512	1,069
Year Five	814	746
Prior Years	2,318	2,224
Revolving Line of Credit	71,924	72,119
Revolving Line of Credit Converted to Term Loan	6,435	6,205
Total Amortized Cost	98,460	95,443
Consumer Segment [Member] | Home Equity [Member] | Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	0
Year Two	0	46
Year Three	0	0
Year Four	0	0
Year Five	0	0
Prior Years	16	21
Revolving Line of Credit	25	62
Revolving Line of Credit Converted to Term Loan	227	195
Total Amortized Cost	268	324
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	0
Year Five	54	0
Prior Years	3	15
Revolving Line of Credit	166	125
Revolving Line of Credit Converted to Term Loan	37	48
Total Amortized Cost	260	188
Consumer Segment [Member] | Other [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	9,637	9,257
Consumer Segment [Member] | Other [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	3,474	4,758
Year Two	3,194	2,693
Year Three	1,896	787
Year Four	433	338
Year Five	128	133
Prior Years	129	129
Revolving Line of Credit	295	412
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	9,549	9,250
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	0
Year Four	0	4
Year Five	2	0
Prior Years	0	0
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	1
Total Amortized Cost	2	5
Consumer Segment [Member] | Other [Member] | Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	2
Year Two	31	0
Year Three	48	0
Year Four	0	0
Year Five	2	0
Prior Years	0	0
Revolving Line of Credit	5	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	$ 86	$ 2