Fair Value Measurement (Assets and Liabilities That are Measured and Not Measured at Fair Value on a Recurring Basis) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013		Dec. 31, 2012
Financial liabilities:
Convertible bonds	$ 1,100.0
Convertible bonds	0		1,100.0
Carrying value
Financial liabilities:
Building financing obligation	7.8		8.0
Convertible bonds	1,100.0
Convertible bonds			1,100.0
Estimated fair value
Financial liabilities:
Convertible bond	1,211.3		1,228.2
Building financing obligation	10.5		10.3
Recurring Basis
Financial assets:
Available-for-sale securities	12.3	[1]	14.2	[1]
Contingent consideration receivable	38.6	[2]	38.3	[2]
Foreign exchange contracts, asset	3.0		1.3
Financial liabilities:
Foreign exchange contracts, liability	2.7		3.0
Contingent consideration payable	585.4	[3]	136.4	[3]
Recurring Basis | Carrying value
Financial assets:
Available-for-sale securities	12.3	[1]	14.2	[1]
Contingent consideration receivable	38.6	[2]	38.3	[2]
Foreign exchange contracts, asset	3.0		1.3
Financial liabilities:
Foreign exchange contracts, liability	2.7		3.0
Contingent consideration payable	585.4	[3]	136.4	[3]
Recurring Basis | Level 1
Financial assets:
Available-for-sale securities	12.3	[1]	14.2	[1]
Contingent consideration receivable	0	[2]	0	[2]
Foreign exchange contracts, asset	0		0
Financial liabilities:
Foreign exchange contracts, liability	0		0
Contingent consideration payable	0	[3]	0	[3]
Recurring Basis | Level 2
Financial assets:
Available-for-sale securities	0	[1]	0	[1]
Contingent consideration receivable	0	[2]	0	[2]
Foreign exchange contracts, asset	3.0		1.3
Financial liabilities:
Foreign exchange contracts, liability	2.7		3.0
Contingent consideration payable	0	[3]	0	[3]
Recurring Basis | Level 3
Financial assets:
Available-for-sale securities	0	[1]	0	[1]
Contingent consideration receivable	38.6	[2]	38.3	[2]
Foreign exchange contracts, asset	0		0
Financial liabilities:
Foreign exchange contracts, liability	0		0
Contingent consideration payable	$ 585.4	[3]	$ 136.4	[3]

[1] Available-for-sale securities are included within Investments in the consolidated balance sheet.

[2] Contingent consideration receivable is included within Prepaid expenses and other current assets and Other non-current assets in the consolidated balance sheet.

[3] Contingent consideration payable is included within Other current liabilities and Other non-current liabilities in the consolidated balance sheet.