Securities (Schedule Of Contractual Maturities) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Sep. 30, 2011
Securities [Abstract]
Available-for-sale Securities, One year or less, Amortized Cost	$ 271,316
Available-for-sale Securities, One year through five years, Amortized Cost	585,866
Available-for-sale Securities, Five years through ten years, Amortized Cost	170,854
Available-for-sale Securities, Ten years and thereafter, Amortized Cost	500,155
Available-for-sale Securities, Amortized Cost	1,528,191	1,443,529
Available-for-sale Securities, One year or less, Estimated Fair Value	271,821
Available-for-sale Securities, One year through five years, Estimated Fair Value	588,643
Available-for-sale Securities, Five years through ten years, Estimated Fair Value	182,375
Available-for-sale Securities, Ten years and thereafter, Estimated Fair Value	527,891
Available-for-sale Securities, Total	1,570,730	1,486,439
Held-to-maturity Securities, One year or less, Amortized Cost	2,429
Held-to-maturity Securities, One year through five years, Amortized Cost	381,204
Held-to-maturity Securities, Five years through ten years, Amortized Cost	452,046
Held-to-maturity Securities, Ten years and thereafter, Amortized Cost	1,293,738
Held-to-maturity Securities, Amortized Cost	2,129,417	2,370,117
Held-to-maturity Securities, One year or less, Estimated Fair Value	2,445
Held-to-maturity Securities, One year through five years, Estimated Fair Value	383,871
Held-to-maturity Securities, Five years through ten years, Estimated Fair Value	470,494
Held-to-maturity Securities, Ten years and thereafter, Estimated Fair Value	1,337,134
Held-to-maturity Securities, Total	2,193,944	2,434,392
Marketable Securities Amortized Cost	3,657,608	3,813,646
Marketable Securities, Estimated fair Value	$ 3,764,674	$ 3,920,831