Financial Instruments (Details 1) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Amortized cost	$ 2,358.4	$ 2,965.0
Gross unrealized gains	6.8	6.0
Gross unrealized losses	(0.4)	(0.7)
Fair value	2,364.8	2,970.3
Marketable equity securities, fair value	2,364.8	2,970.3
Corporate debt securities Current
Debt Securities, Available-for-sale [Line Items]
Amortized cost	963.5	1,057.2
Gross unrealized gains	1.4	1.0
Gross unrealized losses	(0.1)	0.0
Fair value	964.8	1,058.2
Corporate debt securities Non-current
Debt Securities, Available-for-sale [Line Items]
Amortized cost	475.9	633.9
Gross unrealized gains	3.2	3.0
Gross unrealized losses	(0.1)	0.0
Fair value	479.0	636.9
Government securities Current
Debt Securities, Available-for-sale [Line Items]
Amortized cost	389.4	502.9
Gross unrealized gains	0.2	0.4
Gross unrealized losses	0.0	0.0
Fair value	389.6	503.3
Government securities Non-current
Debt Securities, Available-for-sale [Line Items]
Amortized cost	376.4	510.1
Gross unrealized gains	1.4	0.8
Gross unrealized losses	0.0	(0.3)
Fair value	377.8	510.6
Mortgage and other asset backed securities Current
Debt Securities, Available-for-sale [Line Items]
Amortized cost	0.6	0.7
Gross unrealized gains	0.0	0.0
Gross unrealized losses	0.0	0.0
Fair value	0.6	0.7
Mortgage and other asset backed securities Non-current
Debt Securities, Available-for-sale [Line Items]
Amortized cost	152.6	260.2
Gross unrealized gains	0.6	0.8
Gross unrealized losses	(0.2)	(0.4)
Fair value	153.0	260.6
Marketable equity securities
Debt Securities, Available-for-sale [Line Items]
Marketable equity securities, amortized cost	851.7	218.4
Marketable equity securities, gross unrealized gains	63.6	132.1
Marketable equity securities, gross unrealized losses	(46.8)	(13.0)
Marketable equity securities, fair value	$ 868.5	$ 337.5

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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