Condensed Consolidated Cash Flows Statements (USD $) In Millions, unless otherwise specified	6 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Cash flows from operating activities:
Net income	$ 10.0	$ 14.8
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation and amortization	3.5	4.1
Provision for bad debts and impairments	0.7	0.1
Deferred income taxes	(3.5)	(0.3)
Amortization of debt issuance costs and debt discount	0.5	0.6
Amortization of stock-based compensation expense	2.2	3.5
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	(266.3)	(24.9)
Deposits and receivables from exchange-clearing organizations	86.7	(52.4)
Deposits and receivables from broker-dealers, clearing organizations, and counterparties	41.6	(43.4)
Receivable from customers, net	22.4	(58.1)
Notes receivable from customers, net	(27.6)	25.2
Income taxes receivable	2.3	(1.5)
Financial instruments owned, at fair value	(2.7)	(12.6)
Physical commodities inventory	(8.9)	(20.4)
Other assets	(5.0)	3.1
Accounts payable and other accrued liabilities	(16.9)	(3.2)
Payable to customers	177.1	162.1
Payable to broker-dealers, clearing organizations and counterparties	(12.4)	(36.8)
Income taxes payable	3.0	1.4
Financial instruments sold, not yet purchased, at fair value	37.6	62.0
Net cash provided by (used in) operating activities	44.5	14.1
Cash flows from investing activities:
Sale of exchange memberships and common stock	0	10.2
Purchase of property and equipment	(3.1)	(3.1)
Net cash provided by (used in) investing activities	(3.1)	7.1
Cash flows from financing activities:
Net change in payable to lenders under loans and overdrafts	(20.5)	7.7
Payments related to earn-outs on acquisitions	(0.3)	(0.3)
Debt issuance costs	(0.3)	(0.2)
Exercise of stock options	1.2	0.5
Share repurchase	(7.2)	(2.2)
Tax shortfall on stock options and awards	0	(0.3)
Net cash provided by financing activities	(27.1)	5.2
Effect of exchange rates on cash and cash equivalents	(1.2)	(0.7)
Net increase (decrease) in cash and cash equivalents	13.1	25.7
Cash and cash equivalents at beginning of period	156.1	236.3
Cash and cash equivalents at end of period	169.2	262.0
Supplemental disclosure of cash flow information:
Cash paid for interest	5.0	4.7
Income taxes paid, net of cash refunds	1.6	6.0
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	$ 0.3	$ 3.9