Financial Instruments (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Marketable Debt and Equity Securities
Fair Value	$ 1,245.9	$ 3,171.7
Gross Unrealized Gains	0.4	5.6
Gross Unrealized Losses	(0.3)	(1.9)
Amortized Cost	1,245.8	3,168.0
Corporate debt securities Current
Marketable Debt and Equity Securities
Fair Value	100.7	346.9
Gross Unrealized Gains	0	0.3
Gross Unrealized Losses	0	0
Amortized Cost	100.7	346.6
Corporate debt securities Non-current
Marketable Debt and Equity Securities
Fair Value	339.1	654.1
Gross Unrealized Gains	0.4	2.8
Gross Unrealized Losses	(0.1)	(0.6)
Amortized Cost	338.8	651.9
Government securities Current
Marketable Debt and Equity Securities
Fair Value	519.5	783.4
Gross Unrealized Gains	0	0.3
Gross Unrealized Losses	0	0
Amortized Cost	519.5	783.1
Government securities Non-current
Marketable Debt and Equity Securities
Fair Value	155.2	874.4
Gross Unrealized Gains	0	0.8
Gross Unrealized Losses	(0.1)	0
Amortized Cost	155.3	873.6
Mortgage and other asset backed securities Current
Marketable Debt and Equity Securities
Fair Value	0	4.8
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Amortized Cost	0	4.8
Mortgage and other asset backed securities Non-current
Marketable Debt and Equity Securities
Fair Value	131.4	508.1
Gross Unrealized Gains	0	1.4
Gross Unrealized Losses	(0.1)	(1.3)
Amortized Cost	131.5	508.0
Marketable equity securities
Marketable Debt and Equity Securities
Fair Value	11.2	9.0
Gross Unrealized Gains	8.7	3.0
Gross Unrealized Losses	0	0
Amortized Cost	$ 2.5	$ 6.0