Loans And Allowance For Loan Losses (Schedule Of Recorded Investment In Loan Receivables That Are Past Due) (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Sep. 30, 2019
Financing Receivable, Past Due [Line Items]
Total past due	$ 33,478	$ 35,449
Current	13,585,363	13,199,209
Total	13,618,841	13,234,658
30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	10,608	12,482
60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	6,104	6,873
Equal to Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	16,766	16,094
Other Loans
Financing Receivable, Past Due [Line Items]
Total past due	0	0
Current	2,700	3,166
Total	2,700	3,166
Other Loans | 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	0	0
Other Loans | 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	0	0
Other Loans | Equal to Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	0	0
Real Estate Loans
Financing Receivable, Past Due [Line Items]
Total past due	33,478	35,449
Current	13,582,663	13,196,043
Total	13,616,141	13,231,492
Real Estate Loans | 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	10,608	12,482
Real Estate Loans | 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	6,104	6,873
Real Estate Loans | Equal to Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	16,766	16,094
Real Estate Loans | Residential Core
Financing Receivable, Past Due [Line Items]
Total past due	17,622	18,528
Current	11,149,149	10,900,173
Total	11,166,771	10,918,701
Real Estate Loans | Residential Core | 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	4,999	6,824
Real Estate Loans | Residential Core | 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	3,525	4,030
Real Estate Loans | Residential Core | Equal to Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	9,098	7,674
Real Estate Loans | Residential Home Today
Financing Receivable, Past Due [Line Items]
Total past due	6,554	6,937
Current	73,502	77,677
Total	80,056	84,614
Real Estate Loans | Residential Home Today | 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	2,737	2,629
Real Estate Loans | Residential Home Today | 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	987	1,685
Real Estate Loans | Residential Home Today | Equal to Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	2,830	2,623
Real Estate Loans | Home Equity Loans And Lines Of Credit
Financing Receivable, Past Due [Line Items]
Total past due	9,302	9,984
Current	2,334,965	2,191,998
Total	2,344,267	2,201,982
Real Estate Loans | Home Equity Loans And Lines Of Credit | 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	2,872	3,029
Real Estate Loans | Home Equity Loans And Lines Of Credit | 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	1,592	1,158
Real Estate Loans | Home Equity Loans And Lines Of Credit | Equal to Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	4,838	5,797
Real Estate Loans | Construction
Financing Receivable, Past Due [Line Items]
Total past due	0	0
Current	25,047	26,195
Total	25,047	26,195
Real Estate Loans | Construction | 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	0	0
Real Estate Loans | Construction | 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	0	0
Real Estate Loans | Construction | Equal to Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	$ 0	$ 0