Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2013

Assets and Liabilities Measured at Fair Value on Recurring Basis

The following table summarizes assets and liabilities that are measured at fair value on a recurring basis as of March 31, 2013 and December 31, 2012:

	March 31, 2013								December 31, 2012
	Fair Value Asset (Liability)								Fair Value Asset (Liability)
(in millions)	Level 1		Level 2			Total			Level 1		Level 2			Total
Derivatives:
Assets	$	—	$	21.3		$	21.3		$	—	$	10.3		$	10.3
Liabilities		—		(15.1	)		(15.1	)		—		(18.8	)		(18.8	)
Available-for-sale securities		—		20.2			20.2			—		20.0			20.0