Loans Receivable And Allowance For Credit Losses (Classified Loans) (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Sep. 30, 2021
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	$ 276,010	$ 1,953,147
Year Two	1,994,363	1,204,963
Year Three	1,152,663	520,852
Year Four	496,095	455,353
Year Five	428,660	485,640
Prior Years	2,673,582	2,388,212
Revolving Line of Credit	91,767	92,798
Total Amortized Cost	7,113,140	7,100,965
One- to Four-Family Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	218,502	1,590,219
Year Two	1,636,320	1,041,012
Year Three	990,647	416,106
Year Four	392,575	388,651
Year Five	365,415	444,471
Prior Years	2,550,985	2,300,036
Revolving Line of Credit	0	0
Total Amortized Cost	6,154,444	6,180,495
One- to Four-Family Segment [Member] | Originated [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	3,973,279	3,979,536
One- to Four-Family Segment [Member] | Originated [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	153,605	958,080
Year Two	953,530	705,561
Year Three	679,862	326,156
Year Four	309,547	250,846
Year Five	238,567	281,104
Prior Years	1,616,383	1,434,455
Revolving Line of Credit	0	0
Total Amortized Cost	3,951,494	3,956,202
One- to Four-Family Segment [Member] | Originated [Member] | Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	402
Year Two	280	443
Year Three	441	501
Year Four	489	678
Year Five	674	237
Prior Years	7,502	7,805
Revolving Line of Credit	0	0
Total Amortized Cost	9,386	10,066
One- to Four-Family Segment [Member] | Originated [Member] | Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	0
Year Two	0	966
Year Three	965	867
Year Four	862	51
Year Five	151	192
Prior Years	10,421	11,192
Revolving Line of Credit	0	0
Total Amortized Cost	12,399	13,268
One- to Four-Family Segment [Member] | Correspondent Purchased [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	2,015,169	2,026,592
One- to Four-Family Segment [Member] | Correspondent Purchased [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	64,897	630,977
Year Two	682,510	334,042
Year Three	309,379	88,057
Year Four	81,155	136,572
Year Five	125,506	162,938
Prior Years	743,060	664,530
Revolving Line of Credit	0	0
Total Amortized Cost	2,006,507	2,017,116
One- to Four-Family Segment [Member] | Correspondent Purchased [Member] | Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	760
Year Two	0	0
Year Three	0	356
Year Four	353	0
Year Five	517	0
Prior Years	2,706	3,160
Revolving Line of Credit	0	0
Total Amortized Cost	3,576	4,276
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	0	169
Year Four	169	504
Year Five	0	0
Prior Years	4,917	4,527
Revolving Line of Credit	0	0
Total Amortized Cost	5,086	5,200
One- to Four-Family Segment [Member] | Bulk Purchased [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	165,996	174,367
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	161,842	169,519
Revolving Line of Credit	0	0
Total Amortized Cost	161,842	169,519
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	4,154	4,848
Revolving Line of Credit	0	0
Total Amortized Cost	4,154	4,848
Commercial Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	56,341	356,142
Year Two	351,936	160,039
Year Three	158,726	102,185
Year Four	101,321	64,182
Year Five	61,103	40,165
Prior Years	119,427	85,589
Revolving Line of Credit	17,494	17,705
Total Amortized Cost	866,348	826,007
Commercial Segment [Member] | Commercial Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	790,084	759,629
Commercial Segment [Member] | Commercial Real Estate [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	38,103	272,329
Year Two	276,050	149,244
Year Three	149,120	94,972
Year Four	94,674	61,214
Year Five	58,672	38,962
Prior Years	117,858	35,591
Revolving Line of Credit	6,057	5,231
Total Amortized Cost	740,534	657,543
Commercial Segment [Member] | Commercial Real Estate [Member] | Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	50,352
Year Two	47,093	0
Year Three	0	0
Year Four	0	0
Year Five	0	0
Prior Years	0	49,369
Revolving Line of Credit	0	0
Total Amortized Cost	47,093	99,721
Commercial Segment [Member] | Commercial Real Estate [Member] | Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	810
Year Two	944	627
Year Three	594	225
Year Four	225	669
Year Five	662	0
Prior Years	32	34
Revolving Line of Credit	0	0
Total Amortized Cost	2,457	2,365
Commercial Segment [Member] | Commercial and Industrial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	76,264	66,378
Commercial Segment [Member] | Commercial and Industrial [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	18,238	32,651
Year Two	27,849	10,168
Year Three	9,012	6,988
Year Four	6,422	2,213
Year Five	1,683	1,155
Prior Years	1,499	595
Revolving Line of Credit	10,651	11,709
Total Amortized Cost	75,354	65,479
Commercial Segment [Member] | Commercial and Industrial [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
Commercial Segment [Member] | Commercial and Industrial [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	86
Year Five	86	48
Prior Years	38	0
Revolving Line of Credit	786	765
Total Amortized Cost	910	899
Consumer Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	1,167	6,786
Year Two	6,107	3,912
Year Three	3,290	2,561
Year Four	2,199	2,520
Year Five	2,142	1,004
Prior Years	3,170	2,587
Revolving Line of Credit	74,273	75,093
Total Amortized Cost	92,348	94,463
Consumer Segment [Member] | Home Equity [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	84,528	86,385
Consumer Segment [Member] | Home Equity [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	347	3,295
Year Two	3,143	2,218
Year Three	1,857	1,428
Year Four	1,241	1,563
Year Five	1,287	536
Prior Years	2,561	2,473
Revolving Line of Credit	73,106	74,036
Total Amortized Cost	83,542	85,549
Consumer Segment [Member] | Home Equity [Member] | Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	0
Year Two	0	0
Year Three	0	37
Year Four	56	12
Year Five	0	0
Prior Years	0	0
Revolving Line of Credit	265	82
Total Amortized Cost	321	131
Consumer Segment [Member] | Home Equity [Member] | Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	0
Year Two	0	60
Year Three	59	0
Year Four	0	0
Year Five	0	0
Prior Years	85	9
Revolving Line of Credit	521	636
Total Amortized Cost	665	705
Consumer Segment [Member] | Other [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	7,820	8,078
Consumer Segment [Member] | Other [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	820	3,491
Year Two	2,964	1,631
Year Three	1,374	1,086
Year Four	895	944
Year Five	854	465
Prior Years	521	105
Revolving Line of Credit	381	339
Total Amortized Cost	7,809	8,061
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	4
Year Four	0	0
Year Five	0	0
Prior Years	0	0
Revolving Line of Credit	0	0
Total Amortized Cost	0	4
Consumer Segment [Member] | Other [Member] | Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	0
Year Two	0	3
Year Three	0	6
Year Four	7	1
Year Five	1	3
Prior Years	3	0
Revolving Line of Credit	0	0
Total Amortized Cost	$ 11	$ 13