Securities (Schedule Of Amortized Cost And Estimated Fair Value Of Securities Pledged As Collateral) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Sep. 30, 2011
Amortized Cost [Member]
Securities pledged as collateral	$ 596,451	$ 758,583
Estimated Fair Value [Member]
Securities pledged as collateral	626,746	795,001
Repurchase Agreements [Member] | Amortized Cost [Member]
Securities pledged as collateral	408,804	571,016
Repurchase Agreements [Member] | Estimated Fair Value [Member]
Securities pledged as collateral	429,311	597,286
Retail Deposits [Member] | Amortized Cost [Member]
Securities pledged as collateral		44,429
Retail Deposits [Member] | Estimated Fair Value [Member]
Securities pledged as collateral		44,991
Public Unit Deposits [Member] | Amortized Cost [Member]
Securities pledged as collateral	126,161	116,472
Public Unit Deposits [Member] | Estimated Fair Value [Member]
Securities pledged as collateral	133,683	124,785
Federal Reserve Bank [Member] | Amortized Cost [Member]
Securities pledged as collateral	61,486	26,666
Federal Reserve Bank [Member] | Estimated Fair Value [Member]
Securities pledged as collateral	$ 63,752	$ 27,939