Financial Instruments (Details 1) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Marketable Debt and Equity Securities
Fair Value	$ 5,644.5	$ 4,880.9
Gross Unrealized Gains	6.9	0.3
Gross Unrealized Losses	(3.4)	(10.6)
Amortized Cost	5,641.0	4,891.2
Corporate debt securities Current
Marketable Debt and Equity Securities
Fair Value	629.4	394.3
Gross Unrealized Gains	0.2	0.0
Gross Unrealized Losses	(0.3)	(0.5)
Amortized Cost	629.5	394.8
Corporate debt securities Non-current
Marketable Debt and Equity Securities
Fair Value	1,225.7	1,116.6
Gross Unrealized Gains	4.4	0.1
Gross Unrealized Losses	(1.1)	(4.1)
Amortized Cost	1,222.4	1,120.6
Government securities Current
Marketable Debt and Equity Securities
Fair Value	1,823.2	1,723.4
Gross Unrealized Gains	0.4	0.1
Gross Unrealized Losses	(0.2)	(1.1)
Amortized Cost	1,823.0	1,724.4
Government securities Non-current
Marketable Debt and Equity Securities
Fair Value	1,456.7	1,152.5
Gross Unrealized Gains	1.4	0.0
Gross Unrealized Losses	(0.7)	(3.1)
Amortized Cost	1,456.0	1,155.6
Mortgage and other asset backed securities Current
Marketable Debt and Equity Securities
Fair Value	2.1	2.8
Gross Unrealized Gains	0.0	0.0
Gross Unrealized Losses	0.0	0.0
Amortized Cost	2.1	2.8
Mortgage and other asset backed securities Non-current
Marketable Debt and Equity Securities
Fair Value	507.4	491.3
Gross Unrealized Gains	0.5	0.1
Gross Unrealized Losses	(1.1)	(1.8)
Amortized Cost	508.0	493.0
Marketable equity securities
Marketable Debt and Equity Securities
Fair Value	32.8	37.5
Gross Unrealized Gains	2.1	9.2
Gross Unrealized Losses	(2.9)	0.0
Amortized Cost	$ 33.6	$ 28.3