Assets and Liabilities, at Fair Value (Tables)

6 Months Ended

Mar. 31, 2018

Assets and Liabilities, at Fair Value [Abstract]

Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]

The following tables set forth the Company’s financial and nonfinancial assets and liabilities accounted for at fair value, on a recurring basis, as of March 31, 2018 by level in the fair value hierarchy.

	March 31, 2018
(in millions)	Level 1		Level 2		Level 3		Netting and Collateral (1)			Total
Assets:
Unrestricted cash equivalents - certificate of deposits	$	3.7	$	—	$	—	$	—		$	3.7
Commodities warehouse receipts	14.7		—		—		—			14.7
U.S. Treasury obligations	600.9		—		—		—			600.9
Cash, securities and other assets segregated under federal and other regulations	615.6		—		—		—			615.6
U.S. Treasury obligations	648.6		—		—		—			648.6
"To be announced" (TBA) and forward settling securities	—		4.8		—		0.2			5.0
Foreign government obligations	—		6.3		—		—			6.3
Derivatives	3,698.4		21.2		—		(3,730.0		)	(10.4		)
Deposits with and receivables from broker-dealers, clearing organization and counterparties	4,347.0		32.3		—		(3,729.8		)	649.5
Common and preferred stock, ADRs, and GDRs	46.6		2.9		—		—			49.5
Exchangeable foreign ordinary equities, ADRs, and GDRs	17.7		0.5		—		—			18.2
Corporate and municipal bonds	40.9		1.9		—		—			42.8
U.S. Treasury obligations	96.5		—		—		—			96.5
U.S. government agency obligations	—		408.1		—		—			408.1
Foreign government obligations	—		11.3		—		—			11.3
Agency mortgage-backed obligations	—		1,028.9		—		—			1,028.9
Asset-backed obligations	—		41.3		—		—			41.3
Derivatives	1.7		779.2		—		(612.4		)	168.5
Commodities leases	—		47.3		—		(39.3		)	8.0
Commodities warehouse receipts	2.0		—		—		—			2.0
Exchange firm common stock	9.9		—		—		—			9.9
Mutual funds and other	4.7		—		—		—			4.7
Financial instruments owned	220.0		2,321.4		—		(651.7		)	1,889.7
Physical commodities inventory, net	26.9		160.2		—		—			187.1
Total assets at fair value	$	5,213.2	$	2,513.9	$	—	$	(4,381.5	)	$	3,345.6
Liabilities:
TBA and forward settling securities	—		5.7		—		(0.1		)	5.6
Derivatives	3,832.7		34.4		—		(3,867.0		)	0.1
Payable to broker-dealers, clearing organizations and counterparties	3,832.7		40.1		—		(3,867.1		)	5.7
Common and preferred stock, ADRs, and GDRs	52.4		0.5		—		—			52.9
Exchangeable foreign ordinary equities, ADRs, and GDRs	18.3		—		—		—			18.3
Corporate and municipal bonds	0.1		—		—		—			0.1
U.S. Treasury obligations	471.7		—		—		—			471.7
U.S. government agency obligations	—		55.7		—		—			55.7
Agency mortgage-backed obligations	—		0.1		—		—			0.1
Derivatives	—		801.6		—		(625.0		)	176.6
Commodities leases	—		45.6		—		1.9			47.5
Financial instruments sold, not yet purchased	542.5		903.5		—		(623.1		)	822.9
Total liabilities at fair value	$	4,375.2	$	943.6	$	—	$	(4,490.2	)	$	828.6

(1) Represents cash collateral and the impact of netting across the levels of the fair value hierarchy. Netting among positions classified within the same level is included in that level.

The following table sets forth the Company’s financial and nonfinancial assets and liabilities accounted for at fair value, on a recurring basis, as of September 30, 2017 by level in the fair value hierarchy.

	September 30, 2017
(in millions)	Level 1		Level 2		Level 3		Netting and Collateral (1)			Total
Assets:
Unrestricted cash equivalents - certificates of deposits	$	3.8	$	—	$	—	$	—		$	3.8
Commodities warehouse receipts	21.0		—		—		—			21.0
U.S. Treasury obligations	33.5		—		—		—			33.5
Cash, securities and other assets segregated under federal and other regulations	54.5		—		—		—			54.5
U.S. Treasury obligations	244.7		—		—		—			244.7
"To be announced" (TBA) and forward settling securities	—		8.8		—		—			8.8
Foreign government obligations	—		6.4		—		—			6.4
Derivatives	2,608.6		289.1		—		(2,952.9		)	(55.2		)
Deposits with and receivables from broker-dealers, clearing organizations, and counterparties	2,853.3		304.3		—		(2,952.9		)	204.7
Common and preferred stock, ADRs, and GDRs	31.2		3.4		0.1		—			34.7
Exchangeable foreign ordinary equities, ADRs, and GDRs	9.2		1.2		—		—			10.4
Corporate and municipal bonds	28.2		0.9		—		—			29.1
U.S. Treasury obligations	60.0		—		—		—			60.0
U.S. government agency obligations	—		368.9		—		—			368.9
Foreign government obligations	—		10.2		—		—			10.2
Agency mortgage-backed obligations	—		920.9		—		—			920.9
Asset-backed obligations	—		47.3		—		—			47.3
Derivatives	1.3		1,413.4		—		(1,252.6		)	162.1
Commodities leases	—		174.1		—		(138.7		)	35.4
Commodities warehouse receipts	38.5		—		—		—			38.5
Exchange firm common stock	8.3		—		—		—			8.3
Mutual funds and other	6.0		—		—		—			6.0
Financial instruments owned	182.7		2,940.3		0.1		(1,391.3		)	1,731.8
Physical commodities inventory, net	73.2		—		—		—			73.2
Total assets at fair value	$	3,167.5	$	3,244.6	$	0.1	$	(4,344.2	)	$	2,068.0
Liabilities:
Accounts payable and other accrued liabilities - contingent liabilities	$	—	$	—	$	1.0	$	—		$	1.0
TBA and forward settling securities	—		4.9		—		(0.1		)	4.8
Derivatives	2,476.2		292.8		—		(2,769.0		)	—
Payable to broker-dealers, clearing organizations and counterparties	2,476.2		297.7		—		(2,769.1		)	4.8
Common and preferred stock, ADRs, and GDRs	33.7		0.7		—		—			34.4
Exchangeable foreign ordinary equities, ADRs, and GDRs	10.3		0.2		—		—			10.5
Corporate and municipal bonds	0.3		—		—		—			0.3
U.S. Treasury obligations	285.9		—		—		—			285.9
U.S. government agency obligations	—		27.9		—		—			27.9
Agency mortgage-backed obligations	—		0.1		—		—			0.1
Derivatives	—		1,427.2		—		(1,110.2		)	317.0
Commodities leases	—		191.1		—		(149.6		)	41.5
Financial instruments sold, not yet purchased	330.2		1,647.2		—		(1,259.8		)	717.6
Total liabilities at fair value	$	2,806.4	$	1,944.9	$	1.0	$	(4,028.9	)	$	723.4

(1) Represents cash collateral and the impact of netting across the levels of the fair value hierarchy. Netting among positions classified within the same level is included in that level.

Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block]

Information on Level 3 Financial Assets and Liabilities

The following tables set forth a summary of changes in the fair value of the Company’s Level 3 financial assets and liabilities during the three and six months ended March 31, 2018 and 2017, including a summary of unrealized gains (losses) during the respective periods on the Company’s Level 3 financial assets and liabilities held during the periods.

	Level 3 Financial Assets For the Three and Six Months Ended March 31, 2018
(in millions)	Balances at beginning of period		Realized gains (losses) during period		Unrealized gains (losses) during period			Purchases/issuances		Settlements		Transfers in or (out) of Level 3		Balances at end of period
Assets:
Common and preferred stock, ADRs, and GDRs	$	0.1	$	—	$	(0.1	)	$	—	$	—	$	—	$	—
	$	0.1	$	—	$	(0.1	)	$	—	$	—	$	—	$	—

	Level 3 Financial Assets and Financial Liabilities For the Three Months Ended March 31, 2017
(in millions)	Balances at beginning of period		Realized gains (losses) during period		Unrealized gains (losses) during period		Purchases/issuances		Settlements		Transfers in or (out) of Level 3		Balances at end of period
Assets:
Common and preferred stock, ADRs, and GDRs	$	0.2	$	—	$	—	$	—	$	—	$	—	$	0.2
Corporate and municipal bonds	—		—		—		—		—		—		—
	$	0.2	$	—	$	—	$	—	$	—	$	—	$	0.2
(in millions)	Balances at beginning of period		Realized (gains) losses during period		Unrealized (gains) losses during period		Purchases/issuances		Settlements		Transfers in or (out) of Level 3		Balances at end of period
Liabilities:
Contingent liabilities	$	0.8	$	—	$	0.1	$	—	$	—	$	—	$	0.9

	Level 3 Financial Assets and Financial Liabilities For the Six Months Ended March 31, 2017
(in millions)	Balances at beginning of period		Realized gains (losses) during period		Unrealized gains (losses) during period		Purchases/issuances		Settlements			Transfers in or (out) of Level 3		Balances at end of period
Assets:
Common and preferred stock, ADRs, and GDRs	$	0.2	$	—	$	—	$	—	$	—		$	—	$	0.2
Corporate and municipal bonds	3.0		—		—		—		(3.0		)	—		—
	$	3.2	$	—	$	—	$	—	$	(3.0	)	$	—	$	0.2
(in millions)	Balances at beginning of period		Realized (gains) losses during period		Unrealized (gains) losses during period		Purchases/issuances		Settlements			Transfers in or (out) of Level 3		Balances at end of period
Liabilities:
Contingent liabilities	$	0.8	$	—	$	0.1	$	—	$	—		$	—	$	0.9