Financial Instruments (Details 1) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Amortized cost	$ 3,899.5	$ 3,694.0
Gross unrealized gains	9.1	1.3
Gross unrealized losses	(1.2)	(6.0)
Fair value	3,907.4	3,689.3
Marketable equity securities, fair value	3,907.4	3,689.3
Corporate debt securities Current
Debt Securities, Available-for-sale [Line Items]
Amortized cost	1,655.9	1,608.4
Gross unrealized gains	1.5	0.0
Gross unrealized losses	0.0	(0.9)
Fair value	1,657.4	1,607.5
Corporate debt securities Non-current
Debt Securities, Available-for-sale [Line Items]
Amortized cost	1,040.4	854.9
Gross unrealized gains	4.7	0.7
Gross unrealized losses	(0.3)	(3.9)
Fair value	1,044.8	851.7
Government securities Current
Debt Securities, Available-for-sale [Line Items]
Amortized cost	435.6	706.1
Gross unrealized gains	0.5	0.1
Gross unrealized losses	(0.1)	(0.4)
Fair value	436.0	705.8
Government securities Non-current
Debt Securities, Available-for-sale [Line Items]
Amortized cost	431.8	264.0
Gross unrealized gains	0.8	0.1
Gross unrealized losses	(0.4)	(0.3)
Fair value	432.2	263.8
Mortgage and other asset backed securities Current
Debt Securities, Available-for-sale [Line Items]
Amortized cost	0.1	0.1
Gross unrealized gains	0.0	0.0
Gross unrealized losses	0.0	0.0
Fair value	0.1	0.1
Mortgage and other asset backed securities Non-current
Debt Securities, Available-for-sale [Line Items]
Amortized cost	335.7	260.5
Gross unrealized gains	1.6	0.4
Gross unrealized losses	(0.4)	(0.5)
Fair value	336.9	260.4
Marketable equity securities
Debt Securities, Available-for-sale [Line Items]
Marketable equity securities, amortized cost	218.8	496.2
Marketable equity securities, gross unrealized gains	120.7	127.7
Marketable equity securities, gross unrealized losses	(2.8)	(8.5)
Marketable equity securities, fair value	$ 336.7	$ 615.4

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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-Topic 320
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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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