Securities (Schedule Of Contractual Maturities) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Sep. 30, 2016
Investment Holdings [Line Items]
Available-for-sale Securities, Amortized Cost	$ 492,395	$ 517,791
Available-for-sale Securities, Amortized Cost	492,395	517,791
Available-for-sale Securities, Estimated Fair Value	499,792	527,301
Available-for-sale Securities, Estimated Fair Value	499,792	527,301
Held-to-maturity Securities, Amortized Cost	1,022,215	1,100,874
Held-to-maturity Securities, Amortized Cost	1,022,215	1,100,874
Held-to-maturity Securities, Estimated Fair Value	1,027,292	1,122,867
Held-to-maturity securities, Estimated Fair Value	1,027,292	1,122,867
Debt Securities [Member]
Investment Holdings [Line Items]
Available-for-sale Securities, One year or less, Amortized Cost	25,030
Available-for-sale Securities, One year through five years, Amortized Cost	296,216
Available-for-sale Securities, Five years through ten years, Amortized Cost	0
Available-for-sale Securities, Ten years and thereafter, Amortized Cost	2,112
Available-for-sale Securities, Amortized Cost	323,358
Available-for-sale Securities, Amortized Cost	323,358
Available-for-sale Securities, One year or less, Estimated Fair Value	25,032
Available-for-sale Securities, One year through five years, Estimated Fair Value	295,572
Available-for-sale Securities, Five years through ten years, Estimated Fair Value	0
Available-for-sale Securities, Ten years and thereafter, Estimated Fair Value	1,874
Available-for-sale Securities, Estimated Fair Value	322,478
Available-for-sale Securities, Estimated Fair Value	322,478
Held-to-maturity Securities, One year or less, Amortized Cost	7,576
Held-to-maturity Securities, One year through five years, Amortized Cost	20,699
Held-to-maturity Securities, Five years through ten years, Amortized Cost	4,928
Held-to-maturity Securities, Ten years and thereafter, Amortized Cost	0
Held-to-maturity Securities, Amortized Cost	33,203
Held-to-maturity Securities, Amortized Cost	33,203
Held-to-maturity Securities, One year or less, Estimated Fair Value	7,610
Held-to-maturity Securities, One year through five years, Estimated Fair Value	20,565
Held-to-maturity Securities, Five years through ten years, Estimated Fair Value	4,879
Held-to-maturity Securities, Ten years and thereafter, Estimated Fair Value	0
Held-to-maturity Securities, Estimated Fair Value	33,054
Held-to-maturity securities, Estimated Fair Value	33,054
MBS [Member]
Investment Holdings [Line Items]
Available-for-sale Securities, Amortized Cost	169,037	169,442
Available-for-sale Securities, Amortized Cost	169,037	169,442
Available-for-sale Securities, Estimated Fair Value	177,314	178,507
Available-for-sale Securities, Estimated Fair Value	177,314	178,507
Held-to-maturity Securities, Amortized Cost	989,012	1,067,571
Held-to-maturity Securities, Amortized Cost	989,012	1,067,571
Held-to-maturity Securities, Estimated Fair Value	994,238	1,089,214
Held-to-maturity securities, Estimated Fair Value	$ 994,238	$ 1,089,214