v3.26.1
Loans Receivable And Allowance For Credit Losses (Loans, Past Due Aging Analysis) (Details) - USD ($)
$ in Thousands
Mar. 31, 2026
Sep. 30, 2025
Financing Receivable, Past Due [Line Items]    
Total Amortized Cost $ 8,140,804 $ 8,136,000
Financial Asset, Past Due [Member]    
Financing Receivable, Past Due [Line Items]    
Total Amortized Cost 25,419 20,087
Financial Asset, 30 to 89 Days Past Due [Member]    
Financing Receivable, Past Due [Line Items]    
Total Amortized Cost 11,915 12,363
Financial Asset, Equal to or Greater than 90 Days Past Due [Member]    
Financing Receivable, Past Due [Line Items]    
Total Amortized Cost 13,504 7,724
Financial Asset, Not Past Due [Member]    
Financing Receivable, Past Due [Line Items]    
Total Amortized Cost 8,115,385 8,115,913
One- to Four-Family Segment [Member]    
Financing Receivable, Past Due [Line Items]    
Total Amortized Cost 5,716,872 5,914,446
One- to Four-Family Segment [Member] | Originated [Member]    
Financing Receivable, Past Due [Line Items]    
Total Amortized Cost 3,679,335 3,776,443
One- to Four-Family Segment [Member] | Originated [Member] | Financial Asset, Past Due [Member]    
Financing Receivable, Past Due [Line Items]    
Total Amortized Cost 10,730 10,071
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 6,608 7,320
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 4,122 2,751
One- to Four-Family Segment [Member] | Originated [Member] | Financial Asset, Not Past Due [Member]    
Financing Receivable, Past Due [Line Items]    
Total Amortized Cost 3,668,605 3,766,372
One- to Four-Family Segment [Member] | Correspondent Purchased [Member]    
Financing Receivable, Past Due [Line Items]    
Total Amortized Cost 1,927,514 2,023,397
One- to Four-Family Segment [Member] | Correspondent Purchased [Member] | Financial Asset, Past Due [Member]    
Financing Receivable, Past Due [Line Items]    
Total Amortized Cost 7,304 4,508
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 1,972 3,098
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 5,332 1,410
One- to Four-Family Segment [Member] | Correspondent Purchased [Member] | Financial Asset, Not Past Due [Member]    
Financing Receivable, Past Due [Line Items]    
Total Amortized Cost 1,920,210 2,018,889
One- to Four-Family Segment [Member] | Bulk Purchased [Member]    
Financing Receivable, Past Due [Line Items]    
Total Amortized Cost 110,023 114,606
One- to Four-Family Segment [Member] | Bulk Purchased [Member] | Financial Asset, Past Due [Member]    
Financing Receivable, Past Due [Line Items]    
Total Amortized Cost 760 291
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 421 156
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 339 135
One- to Four-Family Segment [Member] | Bulk Purchased [Member] | Financial Asset, Not Past Due [Member]    
Financing Receivable, Past Due [Line Items]    
Total Amortized Cost 109,263 114,315
Commercial Segment [Member]    
Financing Receivable, Past Due [Line Items]    
Total Amortized Cost 2,309,756 2,107,939
Commercial Segment [Member] | Commercial Real Estate [Member]    
Financing Receivable, Past Due [Line Items]    
Total Amortized Cost 2,077,923 1,898,183
Commercial Segment [Member] | Commercial Real Estate [Member] | Financial Asset, Past Due [Member]    
Financing Receivable, Past Due [Line Items]    
Total Amortized Cost 4,210 4,359
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 1,570 1,236
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 2,640 3,123
Commercial Segment [Member] | Commercial Real Estate [Member] | Financial Asset, Not Past Due [Member]    
Financing Receivable, Past Due [Line Items]    
Total Amortized Cost 2,073,713 1,893,824
Commercial Segment [Member] | Commercial and Industrial [Member]    
Financing Receivable, Past Due [Line Items]    
Total Amortized Cost 231,833 209,756
Commercial Segment [Member] | Commercial and Industrial [Member] | Financial Asset, Past Due [Member]    
Financing Receivable, Past Due [Line Items]    
Total Amortized Cost 1,773 243
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 773 32
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 1,000 211
Commercial Segment [Member] | Commercial and Industrial [Member] | Financial Asset, Not Past Due [Member]    
Financing Receivable, Past Due [Line Items]    
Total Amortized Cost 230,060 209,513
Consumer Segment [Member]    
Financing Receivable, Past Due [Line Items]    
Total Amortized Cost 114,176 113,615
Consumer Segment [Member] | Home Equity [Member]    
Financing Receivable, Past Due [Line Items]    
Total Amortized Cost 106,849 105,179
Consumer Segment [Member] | Home Equity [Member] | Financial Asset, Past Due [Member]    
Financing Receivable, Past Due [Line Items]    
Total Amortized Cost 601 490
Consumer Segment [Member] | Home Equity [Member] | Financial Asset, 30 to 89 Days Past Due [Member]    
Financing Receivable, Past Due [Line Items]    
Total Amortized Cost 548 444
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 53 46
Consumer Segment [Member] | Home Equity [Member] | Financial Asset, Not Past Due [Member]    
Financing Receivable, Past Due [Line Items]    
Total Amortized Cost 106,248 104,689
Consumer Segment [Member] | Other [Member]    
Financing Receivable, Past Due [Line Items]    
Total Amortized Cost 7,327 8,436
Consumer Segment [Member] | Other [Member] | Financial Asset, Past Due [Member]    
Financing Receivable, Past Due [Line Items]    
Total Amortized Cost 41 125
Consumer Segment [Member] | Other [Member] | Financial Asset, 30 to 89 Days Past Due [Member]    
Financing Receivable, Past Due [Line Items]    
Total Amortized Cost 23 77
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 18 48
Consumer Segment [Member] | Other [Member] | Financial Asset, Not Past Due [Member]    
Financing Receivable, Past Due [Line Items]    
Total Amortized Cost $ 7,286 $ 8,311