Securities (Schedule Of Contractual Maturities) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Sep. 30, 2019
Investment Holdings [Line Items]
Available-for-sale Securities, Amortized Cost	$ 1,216,776	$ 1,191,455
Available-for-sale Securities, Estimated Fair Value	1,229,587	1,204,863
Debt Securities [Member]
Investment Holdings [Line Items]
Available-for-sale Securities, One year or less, Amortized Cost	81,453
Available-for-sale Securities, One year through five years, Amortized Cost	185,591
Available-for-sale Securities, Five years through ten years, Amortized Cost	25,000
Available-for-sale Securities, Amortized Cost	292,044
Available-for-sale Securities, One year or less, Estimated Fair Value	81,417
Available-for-sale Securities, One year through five years, Estimated Fair Value	185,853
Available-for-sale Securities, Five years through ten years, Estimated Fair Value	25,000
Available-for-sale Securities, Estimated Fair Value	292,270
MBS [Member]
Investment Holdings [Line Items]
Available-for-sale Securities, Amortized Cost	924,732	923,256
Available-for-sale Securities, Estimated Fair Value	$ 937,317	$ 936,487

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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