Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2015

Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]

Financial instruments measured at fair value on a recurring basis

The following tables present financial instruments measured at fair value on a recurring basis:

	September 30, 2015
(in millions)	Level 1		Level 2		Level 3		Total
Assets at Fair Value:
Marketable securities:
U.S. Treasury securities	$	19.2	$	—	$	—	$	19.2
Mutual funds	52.8		—		—		52.8
Equity securities	0.1		—		—		0.1
Asset-backed securities	—		0.3		—		0.3
Total Marketable Securities	72.1		0.3		—		72.4
Performance bonds and guaranty fund contributions:
U.S. Treasury securities (1)	15,105.0		—		—		15,105.0
Equity investments	271.8		—		—		271.8
Total Assets at Fair Value	$	15,448.9	$	0.3	$	—	$	15,449.2
Liabilities at Fair Value:
Contingent consideration	$	—	$	—	$	0.4	$	0.4
Total Liabilities at Fair Value	$	—	$	—	$	0.4	$	0.4

(1) Performance bonds and guaranty fund contributions on the consolidated balance sheet at September 30, 2015 include U.S. Treasury securities purchased with cash collateral.

Reconciliation of assets and liabilities valued at fair value on a recurring basis using significant unobservable inputs (level 3)

The following is a reconciliation of level 3 liabilities valued at fair value on a recurring basis during the first nine months of 2015.

(in millions)	Contingent Consideration
Fair value of liability at December 31, 2014	$	17.7
Realized and unrealized (gains) losses:
Included in other expenses	1.4
Settlements	(18.7		)
Fair value of liability at September 30, 2015	$	0.4

Fair value of Debt Instruments [Table Text Block]

At September 30, 2015, the fair values were as follows:

(in millions)	Fair Value
$750.0 million fixed rate notes due September 2022, stated rate of 3.00%	$	753.9
$750.0 million fixed rate notes due March 2025, stated rate of 3.00%	733.8
$750.0 million fixed rates notes due September 2043, stated rate of 5.30%	851.7