Loans Receivable And Allowance For Credit Losses (Loans, Past Due Aging Analysis) (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Sep. 30, 2023
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	$ 7,971,688	$ 7,994,708
Financial Asset, Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	29,246	25,283
Financial Asset, 30 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	19,024	16,347
Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	10,222	8,936
Financial Asset, Not Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	7,942,442	7,969,425
One- to Four-Family Segment [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	6,539,359	6,606,450
One- to Four-Family Segment [Member] | Originated [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	4,014,490	4,033,028
One- to Four-Family Segment [Member] | Originated [Member] | Financial Asset, Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	11,466	12,360
One- to Four-Family Segment [Member] | Originated [Member] | Financial Asset, 30 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
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, Past Due [Line Items]
Total Amortized Cost	3,741	2,243
One- to Four-Family Segment [Member] | Originated [Member] | Financial Asset, Not Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	4,003,024	4,020,668
One- to Four-Family Segment [Member] | Correspondent Purchased [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	2,389,900	2,435,750
One- to Four-Family Segment [Member] | Correspondent Purchased [Member] | Financial Asset, Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	10,365	8,706
One- to Four-Family Segment [Member] | Correspondent Purchased [Member] | Financial Asset, 30 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
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, Past Due [Line Items]
Total Amortized Cost	4,225	3,454
One- to Four-Family Segment [Member] | Correspondent Purchased [Member] | Financial Asset, Not Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	2,379,535	2,427,044
One- to Four-Family Segment [Member] | Bulk Purchased [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	134,969	137,672
One- to Four-Family Segment [Member] | Bulk Purchased [Member] | Financial Asset, Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	1,529	1,095
One- to Four-Family Segment [Member] | Bulk Purchased [Member] | Financial Asset, 30 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
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, Past Due [Line Items]
Total Amortized Cost	942	942
One- to Four-Family Segment [Member] | Bulk Purchased [Member] | Financial Asset, Not Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	133,440	136,577
Commercial Segment [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	1,325,468	1,283,046
Commercial Segment [Member] | Commercial Real Estate [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	1,211,804	1,170,116
Commercial Segment [Member] | Commercial Real Estate [Member] | Financial Asset, Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	4,690	2,002
Commercial Segment [Member] | Commercial Real Estate [Member] | Financial Asset, 30 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
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, Past Due [Line Items]
Total Amortized Cost	1,116	1,966
Commercial Segment [Member] | Commercial Real Estate [Member] | Financial Asset, Not Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	1,207,114	1,168,114
Commercial Segment [Member] | Commercial and Industrial [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	113,664	112,930
Commercial Segment [Member] | Commercial and Industrial [Member] | Financial Asset, Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	313	277
Commercial Segment [Member] | Commercial and Industrial [Member] | Financial Asset, 30 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
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, Past Due [Line Items]
Total Amortized Cost	82	218
Commercial Segment [Member] | Commercial and Industrial [Member] | Financial Asset, Not Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	113,351	112,653
Consumer Segment [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	106,861	105,212
Consumer Segment [Member] | Home Equity [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	97,191	95,955
Consumer Segment [Member] | Home Equity [Member] | Financial Asset, Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	743	712
Consumer Segment [Member] | Home Equity [Member] | Financial Asset, 30 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
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, Past Due [Line Items]
Total Amortized Cost	116	107
Consumer Segment [Member] | Home Equity [Member] | Financial Asset, Not Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	96,448	95,243
Consumer Segment [Member] | Other [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	9,670	9,257
Consumer Segment [Member] | Other [Member] | Financial Asset, Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	140	131
Consumer Segment [Member] | Other [Member] | Financial Asset, 30 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	140	125
Consumer Segment [Member] | Other [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	0	6
Consumer Segment [Member] | Other [Member] | Financial Asset, Not Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	$ 9,530	$ 9,126