Securities (Schedule Of Contractual Maturities) (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Sep. 30, 2019
Investment Holdings [Line Items]
Available-for-sale Securities, Amortized Cost	$ 1,209,516	$ 1,191,455
Available-for-sale Securities, Estimated Fair Value	1,236,037	1,204,863
Debt Securities [Member]
Investment Holdings [Line Items]
Available-for-sale Securities, One year or less, Amortized Cost	55,179
Available-for-sale Securities, One year through five years, Amortized Cost	206,788
Available-for-sale Securities, Amortized Cost	261,967
Available-for-sale Securities, One year or less, Estimated Fair Value	55,245
Available-for-sale Securities, One year through five years, Estimated Fair Value	207,474
Available-for-sale Securities, Estimated Fair Value	262,719
MBS [Member]
Investment Holdings [Line Items]
Available-for-sale Securities, Amortized Cost	947,549	923,256
Available-for-sale Securities, Estimated Fair Value	$ 973,318	$ 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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