Trading Securities Owned And Trading Securities Sold, But Not Yet Purchased (Components Of Trading Securities Owned And Trading Securities Sold, But Not Yet Purchased) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Sep. 30, 2013	Dec. 31, 2012
Trading securities	$ 801,494		$ 763,608
Trading securities pledged		686,997	607,586
U.S. Government Agency Securities [Member]
Trading securities	88,930		123,758
U.S. Government Securities [Member]
Trading securities	10,594		3,573
Corporate Fixed Income Securities [Member]
Trading securities	483,987		396,878
Corporate Equity Securities [Member]
Trading securities	76,709		35,472
State And Municipal Securities [Member]
Trading securities	141,274		203,927
Securities Owned [Member]
Trading securities	801,494		763,608
Securities Owned [Member] | U.S. Government Agency Securities [Member]
Trading securities owned	88,930		123,758
Securities Owned [Member] | U.S. Government Securities [Member]
Trading securities owned	10,594		3,573
Securities Owned [Member] | Corporate Fixed Income Securities [Member]
Fixed income securities	483,987		396,878
Securities Owned [Member] | Corporate Equity Securities [Member]
Equity securities	76,709		35,472
Securities Owned [Member] | State And Municipal Securities [Member]
State and municipal securities	141,274		203,927
Securities Sold, But Not yet Purchased [Member]
Trading securities	481,214		342,708
Securities Sold, But Not yet Purchased [Member] | U.S. Government Agency Securities [Member]
Trading securities owned	2,068		15
Securities Sold, But Not yet Purchased [Member] | U.S. Government Securities [Member]
Trading securities owned	253,221		162,661
Securities Sold, But Not yet Purchased [Member] | Corporate Fixed Income Securities [Member]
Fixed income securities	135,878		150,698
Securities Sold, But Not yet Purchased [Member] | Corporate Equity Securities [Member]
Equity securities	90,015		29,247
Securities Sold, But Not yet Purchased [Member] | State And Municipal Securities [Member]
State and municipal securities	$ 32		$ 87