Condensed Consolidated Cash Flows Statements (USD $) In Millions, unless otherwise specified	3 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Cash flows from operating activities:
Net income	$ 2.5	$ 13.3
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	1.8	1.8
Provision for bad debts and impairments	0.5	0.4
Deferred income taxes	(3.2)	(0.4)
Amortization of debt issuance costs and debt discount	0.3	0.3
Amortization of stock-based compensation expense	1.1	1.6
Loss on sale of property and equipment	0.2	0
Gain on sale of exchange memberships and common stock	0	(9.2)
Changes in operating assets and liabilities, net:
Cash, securities and other assets segregated under federal and other regulations	233.3	(24.2)
Deposits and receivables from exchange-clearing organizations	(129.8)	141.1
Deposits and receivables from broker-dealers, clearing organizations, and counterparties	4.8	1.4
Receivable from customers, net	18.3	(75.2)
Notes receivable from customers, net	(8.9)	13.7
Income taxes receivable	1.6	4.2
Financial instruments owned, at fair value	(11.9)	11.6
Physical commodities inventory	32.4	(2.3)
Other assets	2.4	(2.0)
Accounts payable and other accrued liabilities	(14.3)	(20.0)
Payable to customers	(107.4)	(8.0)
Payable to broker-dealers, clearing organizations and counterparties	(13.4)	(31.8)
Income taxes payable	0.9	0.8
Financial instruments sold, not yet purchased, at fair value	31.4	12.1
Net cash provided by operating activities	42.6	29.2
Cash flows from investing activities:
Sale of exchange memberships and common stock	0	10.1
Purchase of property and equipment	(1.3)	(1.2)
Net cash (used in) provided by investing activities	(1.3)	8.9
Cash flows from financing activities:
Net change in payable to lenders under loans	(0.8)	23.2
Payments related to earn-outs on acquisitions	(0.3)	(0.3)
Debt issuance costs	(0.3)	0
Exercise of stock options	0.5	0
Share repurchases	(1.3)	(2.0)
Income tax expense on stock options and awards	0	(0.3)
Net cash (used in) provided by financing activities	(2.2)	20.6
Effect of exchange rates on cash and cash equivalents	(0.3)	(0.3)
Net increase in cash and cash equivalents	38.8	58.4
Cash and cash equivalents at beginning of period	156.1	236.3
Cash and cash equivalents at end of period	194.9	294.7
Supplemental disclosure of cash flow information:
Cash paid for interest	2.6	2.5
Income taxes paid, net of cash refunds	1.5	1.3
Supplemental disclosure of non-cash investing and financing activities:
Identified intangible assets and goodwill on acquisitions	0	3.1
Additional consideration payable related to acquisitions	$ 0.2	$ 3.4