Securities (Schedule Of Contractual Maturities) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Sep. 30, 2019
Investment Holdings [Line Items]
Available-for-sale Securities, Amortized Cost	$ 1,529,605	$ 1,191,455
Available-for-sale Securities, Estimated Fair Value	1,560,950	1,204,863
Debt Securities [Member]
Investment Holdings [Line Items]
Available-for-sale Securities, One year or less, Amortized Cost	3,987
Available-for-sale Securities, One year through five years, Amortized Cost	375,696
Available-for-sale Securities, Amortized Cost	379,683
Available-for-sale Securities, One year or less, Estimated Fair Value	4,009
Available-for-sale Securities, One year through five years, Estimated Fair Value	376,138
Available-for-sale Securities, Estimated Fair Value	380,147
MBS [Member]
Investment Holdings [Line Items]
Available-for-sale Securities, Amortized Cost	1,149,922	923,256
Available-for-sale Securities, Estimated Fair Value	$ 1,180,803	$ 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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