Consolidated Cash Flows Statements - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Cash flows from operating activities:
Net income	$ 54.7	$ 55.7	$ 19.3
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	7.8	7.2	7.3
Provision for bad debts and impairments	4.4	7.3	5.5
Deferred income taxes	(0.8)	4.8	(6.8)
Amortization of debt issuance costs and debt discount	1.1	0.9	1.0
Amortization of share-based compensation expense	5.1	3.6	4.3
Loss on sale of property and equipment	0.4	0.5	0.3
Gain on acquisition	(6.2)	0.0	0.0
Gain on sale of exchange memberships and common stock	0.0	(1.2)	0.0
Changes in operating assets and liabilities, net:
Cash, securities and other assets segregated under federal and other regulations	(379.9)	(315.0)	(1.3)
Change in securities purchased under agreements to resell	(285.1)	15.2	0.0
Deposits and receivables from exchange-clearing organizations	10.9	195.1	(159.2)
Deposits and receivables from broker-dealers, clearing organizations, and counterparties	135.7	(150.2)	1.1
Receivable from customers, net	97.8	(169.0)	32.0
Notes receivable, net	59.5	(14.5)	(27.9)
Income taxes receivable	8.2	0.0	4.2
Financial instruments owned, at fair value	(192.9)	(565.0)	(42.6)
Physical commodities inventory	(91.0)	7.1	17.8
Other assets	(17.4)	(16.2)	0.1
Accounts payable and other accrued liabilities	7.5	23.2	1.9
Payable to customers	172.2	332.1	191.5
Payable to broker-dealers, clearing organizations and counterparties	(53.8)	251.1	(5.2)
Income taxes payable	0.3	1.7	5.2
Securities sold under agreements to repurchase	159.8	186.0	0.0
Financial instruments sold, not yet purchased, at fair value	273.9	177.5	84.1
Net cash (used in) provided by operating activities	(27.8)	37.9	132.6
Cash flows from investing activities:
Cash paid for acquisitions, net	(20.0)	(7.8)	0.0
Purchase of exchange memberships and common stock	(0.1)	(0.7)	0.0
Sale of exchange memberships and common stock	0.0	2.1	0.0
Purchase of property and equipment	(15.4)	(9.1)	(4.3)
Net cash used in investing activities	(35.5)	(15.5)	(4.3)
Cash flows from financing activities:
Net change in payable to lenders under loans	142.0	15.5	(38.5)
Payments related to earn-outs on acquisitions	(2.9)	(2.2)	(1.6)
Proceeds from notes payable	0.0	4.0	0.0
Repayment of note payable	0.8	0.4	0.0
Share repurchase	(19.5)	(4.7)	(9.7)
Debt issuance costs	(2.1)	(0.2)	(0.3)
Exercise of stock options	3.5	2.5	1.4
Income tax benefit on stock options and awards	0.8	0.5	(0.1)
Net cash provided by (used in) financing activities	121.0	15.0	(48.8)
Effect of exchange rates on cash and cash equivalents	(9.6)	(0.6)	(4.3)
Net increase in cash and cash equivalents	48.1	36.8	75.2
Cash and cash equivalents at beginning of period	268.1	231.3	156.1
Cash and cash equivalents at end of period	316.2	268.1	231.3
Supplemental disclosure of cash flow information:
Cash paid for interest	26.0	15.8	9.6
Income taxes paid, net of cash refunds	8.5	15.3	3.0
Supplemental disclosure of non-cash investing and financing activities:
Identified intangible assets and goodwill on acquisitions	0.0	1.6	0.5
Additional consideration payable related to acquisitions	(0.4)	1.9	(1.8)
Acquisition of business:
Assets acquired	187.1	1,011.4	0.0
Liabilities acquired	(136.0)	(995.1)	0.0
Total net assets acquired	51.1	16.3	0.0
Deferred consideration payable related to acquisitions	0.0	5.0	0.0
Escrow deposits related to acquisitions	$ 3.4	$ 5.0	$ 0.0