Loans Receivable And Allowance For Credit Losses (Delinquent 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
Financial Asset, Not Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	7,089,681	7,081,450
Financial Asset, 30 to 89 Days Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	12,747	7,861
Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	10,712	11,654
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] | Financial Asset, Not Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	153,605	958,482
Year Two	953,810	706,970
Year Three	680,212	327,408
Year Four	309,531	251,524
Year Five	238,982	281,341
Prior Years	1,626,212	1,445,992
Revolving Line of Credit	0	0
Total Amortized Cost	3,962,352	3,971,717
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	0
Year Three	372	0
Year Four	1,251	51
Year Five	410	0
Prior Years	4,960	4,091
Revolving Line of Credit	0	0
Total Amortized Cost	6,993	4,142
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	0
Year Three	684	116
Year Four	116	0
Year Five	0	192
Prior Years	3,134	3,369
Revolving Line of Credit	0	0
Total Amortized Cost	3,934	3,677
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] | Financial Asset, Not Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	64,897	630,977
Year Two	681,753	334,042
Year Three	309,379	88,413
Year Four	81,508	136,572
Year Five	124,031	162,017
Prior Years	745,230	668,685
Revolving Line of Credit	0	0
Total Amortized Cost	2,006,798	2,020,706
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	760
Year Two	757	0
Year Three	0	0
Year Four	0	0
Year Five	1,992	921
Prior Years	2,464	948
Revolving Line of Credit	0	0
Total Amortized Cost	5,213	2,629
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	169
Year Four	169	504
Year Five	0	0
Prior Years	2,989	2,584
Revolving Line of Credit	0	0
Total Amortized Cost	3,158	3,257
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] | 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	163,873	170,809
Revolving Line of Credit	0	0
Total Amortized Cost	163,873	170,809
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	155	555
Revolving Line of Credit	0	0
Total Amortized Cost	155	555
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	1,968	3,003
Revolving Line of Credit	0	0
Total Amortized Cost	1,968	3,003
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] | Financial Asset, Not Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	38,103	323,491
Year Two	323,897	149,244
Year Three	149,120	94,972
Year Four	94,674	61,651
Year Five	59,102	38,962
Prior Years	117,858	84,957
Revolving Line of Credit	6,057	5,231
Total Amortized Cost	788,811	758,508
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	0
Year Two	190	0
Year Three	0	0
Year Four	0	0
Year Five	0	0
Prior Years	32	37
Revolving Line of Credit	0	0
Total Amortized Cost	222	37
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	0	627
Year Three	594	225
Year Four	225	232
Year Five	232	0
Prior Years	0	0
Revolving Line of Credit	0	0
Total Amortized Cost	1,051	1,084
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] | Financial Asset, Not Past Due [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	2,212
Year Five	1,683	1,155
Prior Years	1,499	595
Revolving Line of Credit	11,437	12,474
Total Amortized Cost	76,140	66,243
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	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] | 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	87
Year Five	86	48
Prior Years	38	0
Revolving Line of Credit	0	0
Total Amortized Cost	124	135
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] | Financial Asset, Not Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	347	3,295
Year Two	3,143	2,218
Year Three	1,857	1,465
Year Four	1,297	1,575
Year Five	1,287	536
Prior Years	2,559	2,357
Revolving Line of Credit	73,423	73,958
Total Amortized Cost	83,913	85,404
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	0	0
Year Three	0	0
Year Four	0	0
Year Five	0	0
Prior Years	7	121
Revolving Line of Credit	142	375
Total Amortized Cost	149	496
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	60
Year Three	59	0
Year Four	0	0
Year Five	0	0
Prior Years	80	4
Revolving Line of Credit	327	421
Total Amortized Cost	466	485
Consumer Segment [Member] | Other [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	7,820	8,078
Consumer Segment [Member] | Other [Member] | Financial Asset, Not Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	820	3,491
Year Two	2,961	1,631
Year Three	1,365	1,088
Year Four	895	944
Year Five	854	465
Prior Years	518	105
Revolving Line of Credit	381	339
Total Amortized Cost	7,794	8,063
Consumer Segment [Member] | Other [Member] | Financial Asset, 30 to 89 Days Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	0
Year Two	3	0
Year Three	9	2
Year Four	0	0
Year Five	0	0
Prior Years	3	0
Revolving Line of Credit	0	0
Total Amortized Cost	15	2
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	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