Loans Receivable And Allowance For Credit Losses (Summary Of Loan Portfolio Segment Disaggregated By The Company's Impairment Method) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Sep. 30, 2012
Financing Receivable, Impaired [Line Items]
Recorded investment of loans collectively evaluated for impairment	$ 5,627,334	$ 5,592,205
Recorded investment of loans individually evaluated for impairment	23,220	26,978
Recorded Investment Financing Receivable	5,650,554	5,619,183
ACL for loans collectively evaluated for impairment	10,477	11,100
One-To Four-Family Loans - Originated [Member]
Financing Receivable, Impaired [Line Items]
Recorded investment of loans collectively evaluated for impairment	4,672,011	4,602,969
Recorded investment of loans individually evaluated for impairment	7,454	10,729
Recorded Investment Financing Receivable	4,679,465	4,613,698
ACL for loans collectively evaluated for impairment	5,639	6,074
One-To Four-Family Loans - Purchased [Member]
Financing Receivable, Impaired [Line Items]
Recorded investment of loans collectively evaluated for impairment	744,630	774,734
Recorded investment of loans individually evaluated for impairment	15,195	15,339
Recorded Investment Financing Receivable	759,825	790,073
ACL for loans collectively evaluated for impairment	4,290	4,453
One-To Four-Family Loans [Member]
Financing Receivable, Impaired [Line Items]
Recorded investment of loans collectively evaluated for impairment	5,416,641	5,377,703
Recorded investment of loans individually evaluated for impairment	22,649	26,068
Recorded Investment Financing Receivable	5,439,290	5,403,771
ACL for loans collectively evaluated for impairment	9,929	10,527
Multi-Family And Commercial [Member]
Financing Receivable, Impaired [Line Items]
Recorded investment of loans collectively evaluated for impairment	60,717	59,562
Recorded Investment Financing Receivable	60,717	59,562
ACL for loans collectively evaluated for impairment	201	219
Consumer [Member]
Financing Receivable, Impaired [Line Items]
Recorded investment of loans collectively evaluated for impairment	149,976	154,940
Recorded investment of loans individually evaluated for impairment	571	910
Recorded Investment Financing Receivable	150,547	155,850
ACL for loans collectively evaluated for impairment	$ 347	$ 354