Description of Business and Significant Accounting Policies Cash, Cash Equivalents, Securities (Details) (USD $)	12 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2010 Rate
Cash, Cash Equivalents, and Securities Disclosed in Significant Accounting Policies [Abstract]
Convertible Debt Holder's Principal Balance			$ 16,700,000
Cash Held at Banks and Money Market Funds - Segregated	284,700,000	96,700,000
US Government Obligations and other securities	50,500,000	3,700,000
Commodities Warehouse Receipts	22,300,000	19,000,000
Cash and Cash Equivalents - Deposits and Receivables	400,000,000	1,200,000,000
US Government Securities and Other Securities - Deposits and Receivables	1,300,000,000	500,000,000
Secured Deficits - US T-bills	800,000	400,000
Secured Deficits - Commodities Warehouse Receipts	7,500,000	16,200,000
Proceeds from Sale of Property, Plant, and Equipment	1,500,000
Gain (Loss) on Sale of Property Plant Equipment	900,000
Acquisition of Memberships in Exchanges		3,400,000
Memberships in Exchanges Owned	10,500,000	10,300,000
Proceeds from Shares of Exchanges Sold		1,200,000
Fair Value of Exchange Memberships	8,900,000	10,500,000
Debt Instrument, Interest Rate, Stated Percentage			7.625%
Accrued interest on convertible		$ 200,000
Stock Issued During Period, Shares, Conversion of Convertible Securities		778,703