Loans Receivable and Allowance for Credit Losses (Financial Effect of Modifications) (Details)	3 Months Ended		6 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2025	Mar. 31, 2024
One- to Four-Family Segment [Member] \| Originated [Member]
Financing Receivable, Modified [Line Items]
Financing Receivable, Modified, Payment Deferral, Period	8 months	4 months	8 months	4 months
Financing Receivable, Modified, Weighted Average Term Increase from Modification	20 months	39 months	18 months	31 months
One- to Four-Family Segment [Member] \| Correspondent Purchased [Member]
Financing Receivable, Modified [Line Items]
Financing Receivable, Modified, Payment Deferral, Period	9 months	5 months	9 months	4 months
Financing Receivable, Modified, Weighted Average Term Increase from Modification	34 months	20 months	34 months	17 months
Commercial Segment [Member] \| Commercial Real Estate [Member]
Financing Receivable, Modified [Line Items]
Financing Receivable, Modified, Payment Deferral, Period	9 months	26 months	9 months	26 months
Financing Receivable, Modified, Weighted Average Term Increase from Modification		26 months		26 months
Commercial Segment [Member] \| Commercial and Industrial [Member]
Financing Receivable, Modified [Line Items]
Financing Receivable, Modified, Payment Deferral, Period		6 months		6 months
Financing Receivable, Modified, Weighted Average Term Increase from Modification	3 months	6 months	3 months	6 months
Consumer Segment [Member] \| Home Equity [Member]
Financing Receivable, Modified [Line Items]
Financing Receivable, Modified, Payment Deferral, Period			7 months
Financing Receivable, Modified, Weighted Average Term Increase from Modification	14 months		14 months