Debt (Summary of Cash Convertible Notes) (Details) - USD ($) $ in Millions		Jun. 30, 2015	Dec. 31, 2014	Sep. 15, 2008
Debt Instrument [Line Items]
Net debt carrying amount (a)		$ 2,099.2	$ 2,405.7
Cash Convertible Notes | Convertible Debt
Debt Instrument [Line Items]
Outstanding principal		412.5	573.1	$ 575.0
Equity component carrying amount		1,689.3	1,853.5
Unamortized discount		(4.5)	(21.0)
Net debt carrying amount (a)	[1]	2,097.3	2,405.6
Cash Convertible Notes | Call Options
Debt Instrument [Line Items]
Purchased call options (b)	[2]	$ 1,689.3	$ 1,853.5

[1] As of June 30, 2015 and December 31, 2014, the cash convertible notes were classified as current portion of long-term debt on the Condensed Consolidated Balance Sheets.

[2] As of June 30, 2015 and December 31, 2014, purchased call options were classified as prepaid expenses and other current assets on the Condensed Consolidated Balance Sheets.