Loans Receivable And Allowance For Credit Losses (Loans, Past Due Aging Analysis) (Details) - USD ($) $ in Thousands	Jun. 30, 2025	Sep. 30, 2024
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	$ 8,046,362	$ 7,930,373
Financial Asset, Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	24,076	25,630
Financial Asset, 30 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	16,032	16,049
Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	8,044	9,581
Financial Asset, Not Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	8,022,286	7,904,743
One- to Four-Family Segment [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	6,028,858	6,316,779
One- to Four-Family Segment [Member] | Originated [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	3,828,903	3,950,046
One- to Four-Family Segment [Member] | Originated [Member] | Financial Asset, Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	11,755	11,135
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	9,590	8,864
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	2,165	2,271
One- to Four-Family Segment [Member] | Originated [Member] | Financial Asset, Not Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	3,817,148	3,938,911
One- to Four-Family Segment [Member] | Correspondent Purchased [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	2,082,861	2,239,143
One- to Four-Family Segment [Member] | Correspondent Purchased [Member] | Financial Asset, Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	4,594	7,179
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	2,830	3,089
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	1,764	4,090
One- to Four-Family Segment [Member] | Correspondent Purchased [Member] | Financial Asset, Not Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	2,078,267	2,231,964
One- to Four-Family Segment [Member] | Bulk Purchased [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	117,094	127,590
One- to Four-Family Segment [Member] | Bulk Purchased [Member] | Financial Asset, Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	294	1,608
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	157	69
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	137	1,539
One- to Four-Family Segment [Member] | Bulk Purchased [Member] | Financial Asset, Not Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	116,800	125,982
Commercial Segment [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	1,904,494	1,503,732
Commercial Segment [Member] | Commercial Real Estate [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	1,720,372	1,374,054
Commercial Segment [Member] | Commercial Real Estate [Member] | Financial Asset, Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	5,042	4,156
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	1,654	2,993
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	3,388	1,163
Commercial Segment [Member] | Commercial Real Estate [Member] | Financial Asset, Not Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	1,715,330	1,369,898
Commercial Segment [Member] | Commercial and Industrial [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	184,122	129,678
Commercial Segment [Member] | Commercial and Industrial [Member] | Financial Asset, Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	1,579	473
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	1,166	391
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	413	82
Commercial Segment [Member] | Commercial and Industrial [Member] | Financial Asset, Not Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	182,543	129,205
Consumer Segment [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	113,010	109,862
Consumer Segment [Member] | Home Equity [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	103,901	100,247
Consumer Segment [Member] | Home Equity [Member] | Financial Asset, Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	634	809
Consumer Segment [Member] | Home Equity [Member] | Financial Asset, 30 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	525	471
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	109	338
Consumer Segment [Member] | Home Equity [Member] | Financial Asset, Not Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	103,267	99,438
Consumer Segment [Member] | Other [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	9,109	9,615
Consumer Segment [Member] | Other [Member] | Financial Asset, Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	178	270
Consumer Segment [Member] | Other [Member] | Financial Asset, 30 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	110	172
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	68	98
Consumer Segment [Member] | Other [Member] | Financial Asset, Not Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Amortized Cost	$ 8,931	$ 9,345