Financial Instruments (Schedule of Fair Value Measurement) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Noncurrent investments:
Noncurrent investments	$ 2,966.8	$ 1,962.4
Carrying Amount
Statement [Line Items]
Cash equivalents	2,097.9	1,025.4
Short-term investments:
Debt securities	24.2	101.0
Noncurrent investments:
Equity investments without readily determinable fair values	373.9	405.0
Noncurrent investments	2,966.8	1,962.4
Cost
Statement [Line Items]
Cash equivalents	2,097.9	1,025.4
Fair Value
Statement [Line Items]
Cash equivalents	2,097.9	1,025.4
Fair Value \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Statement [Line Items]
Cash equivalents	2,097.9	1,025.4
Fair Value \| Significant Other Observable Inputs (Level 2)
Statement [Line Items]
Cash equivalents	0.0	0.0
Fair Value \| Significant Unobservable Inputs (Level 3)
Statement [Line Items]
Cash equivalents	0.0	0.0
U.S. government and agency securities \| Carrying Amount
Short-term investments:
Debt securities	9.9	7.2
Noncurrent investments:
Noncurrent investments, debt securities	78.7	77.2
U.S. government and agency securities \| Cost
Short-term investments:
Debt securities	9.9	7.2
Noncurrent investments:
Noncurrent investments, debt securities	74.3	76.3
U.S. government and agency securities \| Fair Value
Short-term investments:
Debt securities	9.9	7.2
Noncurrent investments:
Noncurrent investments, debt securities	78.7	77.2
U.S. government and agency securities \| Fair Value \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Short-term investments:
Debt securities	9.9	7.2
Noncurrent investments:
Noncurrent investments, debt securities	78.7	77.2
U.S. government and agency securities \| Fair Value \| Significant Other Observable Inputs (Level 2)
Short-term investments:
Debt securities	0.0	0.0
Noncurrent investments:
Noncurrent investments, debt securities	0.0	0.0
U.S. government and agency securities \| Fair Value \| Significant Unobservable Inputs (Level 3)
Short-term investments:
Debt securities	0.0	0.0
Noncurrent investments:
Noncurrent investments, debt securities	0.0	0.0
Corporate debt securities \| Carrying Amount
Short-term investments:
Debt securities	2.8	81.4
Noncurrent investments:
Noncurrent investments, debt securities	137.0	271.1
Corporate debt securities \| Cost
Short-term investments:
Debt securities	2.8	81.1
Noncurrent investments:
Noncurrent investments, debt securities	126.8	267.8
Corporate debt securities \| Fair Value
Short-term investments:
Debt securities	2.8	81.4
Noncurrent investments:
Noncurrent investments, debt securities	137.0	271.1
Corporate debt securities \| Fair Value \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Short-term investments:
Debt securities	0.0	0.0
Noncurrent investments:
Noncurrent investments, debt securities	0.0	0.0
Corporate debt securities \| Fair Value \| Significant Other Observable Inputs (Level 2)
Short-term investments:
Debt securities	2.8	81.4
Noncurrent investments:
Noncurrent investments, debt securities	137.0	271.1
Corporate debt securities \| Fair Value \| Significant Unobservable Inputs (Level 3)
Short-term investments:
Debt securities	0.0	0.0
Noncurrent investments:
Noncurrent investments, debt securities	0.0	0.0
Asset-backed securities \| Carrying Amount
Short-term investments:
Debt securities	1.2	2.6
Noncurrent investments:
Noncurrent investments, debt securities	24.3	30.0
Asset-backed securities \| Cost
Short-term investments:
Debt securities	1.2	2.6
Noncurrent investments:
Noncurrent investments, debt securities	23.7	29.6
Asset-backed securities \| Fair Value
Short-term investments:
Debt securities	1.2	2.6
Noncurrent investments:
Noncurrent investments, debt securities	24.3	30.0
Asset-backed securities \| Fair Value \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Short-term investments:
Debt securities	0.0	0.0
Noncurrent investments:
Noncurrent investments, debt securities	0.0	0.0
Asset-backed securities \| Fair Value \| Significant Other Observable Inputs (Level 2)
Short-term investments:
Debt securities	1.2	2.6
Noncurrent investments:
Noncurrent investments, debt securities	24.3	30.0
Asset-backed securities \| Fair Value \| Significant Unobservable Inputs (Level 3)
Short-term investments:
Debt securities	0.0	0.0
Noncurrent investments:
Noncurrent investments, debt securities	0.0	0.0
Other securities \| Carrying Amount
Short-term investments:
Debt securities	10.3	9.8
Other securities \| Cost
Short-term investments:
Debt securities	10.3	9.8
Other securities \| Fair Value
Short-term investments:
Debt securities	10.3	9.8
Other securities \| Fair Value \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Short-term investments:
Debt securities	0.0	0.0
Other securities \| Fair Value \| Significant Other Observable Inputs (Level 2)
Short-term investments:
Debt securities	0.0	0.0
Other securities \| Fair Value \| Significant Unobservable Inputs (Level 3)
Short-term investments:
Debt securities	10.3	9.8
Mortgage-backed securities \| Carrying Amount
Noncurrent investments:
Noncurrent investments, debt securities	106.4	101.1
Mortgage-backed securities \| Cost
Noncurrent investments:
Noncurrent investments, debt securities	101.4	99.6
Mortgage-backed securities \| Fair Value
Noncurrent investments:
Noncurrent investments, debt securities	106.4	101.1
Mortgage-backed securities \| Fair Value \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Noncurrent investments:
Noncurrent investments, debt securities	0.0	0.0
Mortgage-backed securities \| Fair Value \| Significant Other Observable Inputs (Level 2)
Noncurrent investments:
Noncurrent investments, debt securities	106.4	101.1
Mortgage-backed securities \| Fair Value \| Significant Unobservable Inputs (Level 3)
Noncurrent investments:
Noncurrent investments, debt securities	0.0	0.0
Other securities \| Carrying Amount
Noncurrent investments:
Equity securities	110.5	60.0
Other securities \| Cost
Noncurrent investments:
Equity securities	31.8	27.4
Other securities \| Fair Value
Noncurrent investments:
Equity securities	110.5	60.0
Other securities \| Fair Value \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Noncurrent investments:
Equity securities	0.0	0.0
Other securities \| Fair Value \| Significant Other Observable Inputs (Level 2)
Noncurrent investments:
Equity securities	0.0	0.0
Other securities \| Fair Value \| Significant Unobservable Inputs (Level 3)
Noncurrent investments:
Equity securities	110.5	60.0
Marketable equity securities \| Carrying Amount
Noncurrent investments:
Equity securities	1,664.2	718.6
Marketable equity securities \| Cost
Noncurrent investments:
Equity securities	311.6	254.4
Marketable equity securities \| Fair Value
Noncurrent investments:
Equity securities	1,664.2	718.6
Marketable equity securities \| Fair Value \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Noncurrent investments:
Equity securities	1,664.2	718.6
Marketable equity securities \| Fair Value \| Significant Other Observable Inputs (Level 2)
Noncurrent investments:
Equity securities	0.0	0.0
Marketable equity securities \| Fair Value \| Significant Unobservable Inputs (Level 3)
Noncurrent investments:
Equity securities	0.0	0.0
Equity method investments \| Carrying Amount
Noncurrent investments:
Equity method investments	$ 471.8	$ 299.4

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