Loans Receivable And Allowance For Credit Losses (Delinquent Loans) (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Sep. 30, 2023
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	$ 184,495	$ 1,124,730
Year Two	1,122,186	1,450,679
Year Three	1,452,300	1,709,273
Year Four	1,622,110	904,106
Year Five	886,526	403,494
Prior Years	2,585,414	2,285,008
Revolving Line of Credit	112,322	110,969
Revolving Line of Credit Converted to Term Loan	6,335	6,449
Total Amortized Cost	7,971,688	7,994,708
Financial Asset, Not Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	7,942,442	7,969,425
Financial Asset, 30 to 89 Days Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	19,024	16,347
Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	10,222	8,936
One- to Four-Family Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	52,270	665,253
Year Two	668,235	1,117,986
Year Three	1,109,900	1,485,849
Year Four	1,460,130	817,322
Year Five	801,740	317,676
Prior Years	2,447,084	2,202,364
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	6,539,359	6,606,450
One- to Four-Family Segment [Member] | Originated [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	4,014,490	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	50,552	318,211
Year Two	323,563	598,283
Year Three	601,737	875,563
Year Four	859,737	567,975
Year Five	557,404	253,546
Prior Years	1,610,031	1,407,090
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	4,003,024	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	0	898
Year Three	192	644
Year Four	544	1,437
Year Five	769	820
Prior Years	6,220	5,960
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	7,725	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	0	0
Year Four	471	0
Year Five	489	209
Prior Years	2,781	1,587
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	3,741	2,243
One- to Four-Family Segment [Member] | Correspondent Purchased [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	2,389,900	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	1,718	346,084
Year Two	343,899	518,650
Year Three	505,799	608,573
Year Four	596,983	247,346
Year Five	243,078	62,652
Prior Years	688,058	643,739
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	2,379,535	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	773	0
Year Three	610	1,069
Year Four	2,395	564
Year Five	0	449
Prior Years	2,362	2,862
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	6,140	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	1,562	0
Year Four	0	0
Year Five	0	0
Prior Years	2,663	3,454
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	4,225	3,454
One- to Four-Family Segment [Member] | Bulk Purchased [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	134,969	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	133,440	136,577
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	133,440	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	587	153
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	587	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	942	942
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	942	942
Commercial Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	128,122	449,216
Year Two	444,429	324,330
Year Three	334,471	220,682
Year Four	159,617	85,373
Year Five	83,499	84,939
Prior Years	135,396	80,255
Revolving Line of Credit	39,934	38,251
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	1,325,468	1,283,046
Commercial Segment [Member] | Commercial Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	1,211,804	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	123,381	404,867
Year Two	399,539	301,164
Year Three	313,127	208,942
Year Four	148,827	81,478
Year Five	80,136	82,027
Prior Years	130,629	79,188
Revolving Line of Credit	11,475	10,448
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	1,207,114	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	946	36
Year Two	1,129	0
Year Three	0	0
Year Four	0	0
Year Five	58	0
Prior Years	1,191	0
Revolving Line of Credit	250	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	3,574	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	67	0
Year Three	0	0
Year Four	0	594
Year Five	594	219
Prior Years	455	237
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	1,116	1,966
Commercial Segment [Member] | Commercial and Industrial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	113,664	112,930
Commercial Segment [Member] | Commercial and Industrial [Member] | Financial Asset, Not Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	3,795	43,397
Year Two	43,463	23,166
Year Three	21,344	11,740
Year Four	10,790	3,228
Year Five	2,711	2,690
Prior Years	3,039	748
Revolving Line of Credit	28,209	27,684
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	113,351	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	231	0
Year Three	0	0
Year Four	0	0
Year Five	0	2
Prior Years	0	0
Revolving Line of Credit	0	57
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	231	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	4,103	10,261
Year Two	9,522	8,363
Year Three	7,929	2,742
Year Four	2,363	1,411
Year Five	1,287	879
Prior Years	2,934	2,389
Revolving Line of Credit	72,388	72,718
Revolving Line of Credit Converted to Term Loan	6,335	6,449
Total Amortized Cost	106,861	105,212
Consumer Segment [Member] | Home Equity [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	97,191	95,955
Consumer Segment [Member] | Home Equity [Member] | Financial Asset, Not Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	2,552	5,428
Year Two	5,341	5,631
Year Three	5,452	1,955
Year Four	1,706	990
Year Five	1,031	746
Prior Years	2,676	2,195
Revolving Line of Credit	71,483	71,986
Revolving Line of Credit Converted to Term Loan	6,207	6,312
Total Amortized Cost	96,448	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	0	39
Year Three	38	0
Year Four	17	79
Year Five	0	0
Prior Years	64	50
Revolving Line of Credit	473	239
Revolving Line of Credit Converted to Term Loan	35	125
Total Amortized Cost	627	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	0	0
Prior Years	3	15
Revolving Line of Credit	20	81
Revolving Line of Credit Converted to Term Loan	93	11
Total Amortized Cost	116	107
Consumer Segment [Member] | Other [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	9,670	9,257
Consumer Segment [Member] | Other [Member] | Financial Asset, Not Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	1,551	4,737
Year Two	4,146	2,613
Year Three	2,368	765
Year Four	618	338
Year Five	250	132
Prior Years	190	129
Revolving Line of Credit	407	412
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	9,530	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	0	17
Year Two	35	80
Year Three	71	22
Year Four	22	4
Year Five	6	1
Prior Years	1	0
Revolving Line of Credit	5	0
Revolving Line of Credit Converted to Term Loan	0	1
Total Amortized Cost	140	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	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	$ 6