Financial Instruments (Fair Value of Financial Instruments) (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments without readily determinable fair values		$ 405.0
Noncurrent investments	$ 2,148.7	1,962.4
Carrying Amount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	417.1	1,025.4
Short-term investments, debt securities	78.4	101.0
Equity investments without readily determinable fair values	426.3
Noncurrent investments	2,148.7	1,962.4
Short-term commercial paper borrowings	(3,243.1)	(1,494.2)
Long-term debt, including current portion	(13,987.2)	(13,823.0)
Cost
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	417.1	1,025.4
Estimate of Fair Value Measurement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	417.1	1,025.4
Short-term commercial paper borrowings	(3,239.0)	(1,491.6)
Long-term debt, including current portion	(15,119.0)	(15,150.0)
Estimate of Fair Value Measurement | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	417.1	1,025.4
Short-term commercial paper borrowings	0.0	0.0
Long-term debt, including current portion	0.0	0.0
Estimate of Fair Value Measurement | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0.0	0.0
Short-term commercial paper borrowings	(3,239.0)	(1,491.6)
Long-term debt, including current portion	(15,119.0)	(15,150.0)
Estimate of Fair Value Measurement | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0.0	0.0
Short-term commercial paper borrowings	0.0	0.0
Long-term debt, including current portion	0.0	0.0
U.S. government and agency securities | Carrying Amount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments, debt securities	9.3	7.2
Noncurrent investments, debt securities	81.2	77.2
U.S. government and agency securities | Cost
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments, debt securities	9.2	7.2
Noncurrent investments, debt securities	77.4	76.3
U.S. government and agency securities | Estimate of Fair Value Measurement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments, debt securities	9.3	7.2
Noncurrent investments, debt securities	81.2	77.2
U.S. government and agency securities | Estimate of Fair Value Measurement | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments, debt securities	9.3	7.2
Noncurrent investments, debt securities	81.2	77.2
U.S. government and agency securities | Estimate of Fair Value Measurement | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments, debt securities	0.0	0.0
Noncurrent investments, debt securities	0.0	0.0
U.S. government and agency securities | Estimate of Fair Value Measurement | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments, debt securities	0.0	0.0
Noncurrent investments, debt securities	0.0	0.0
Corporate debt securities | Carrying Amount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments, debt securities	61.2	81.4
Noncurrent investments, debt securities	230.6	271.1
Corporate debt securities | Cost
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments, debt securities	62.7	81.1
Noncurrent investments, debt securities	241.0	267.8
Corporate debt securities | Estimate of Fair Value Measurement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments, debt securities	61.2	81.4
Noncurrent investments, debt securities	230.6	271.1
Corporate debt securities | Estimate of Fair Value Measurement | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments, debt securities	0.0	0.0
Noncurrent investments, debt securities	0.0	0.0
Corporate debt securities | Estimate of Fair Value Measurement | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments, debt securities	61.2	81.4
Noncurrent investments, debt securities	230.6	271.1
Corporate debt securities | Estimate of Fair Value Measurement | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments, debt securities		0.0
Noncurrent investments, debt securities	0.0	0.0
Asset-backed securities | Carrying Amount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments, debt securities	2.5	2.6
Noncurrent investments, debt securities	30.1	30.0
Asset-backed securities | Cost
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments, debt securities	2.5	2.6
Noncurrent investments, debt securities	30.1	29.6
Asset-backed securities | Estimate of Fair Value Measurement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments, debt securities	2.5	2.6
Noncurrent investments, debt securities	30.1	30.0
Asset-backed securities | Estimate of Fair Value Measurement | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments, debt securities	0.0	0.0
Noncurrent investments, debt securities	0.0	0.0
Asset-backed securities | Estimate of Fair Value Measurement | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments, debt securities	2.5	2.6
Noncurrent investments, debt securities	30.1	30.0
Asset-backed securities | Estimate of Fair Value Measurement | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments, debt securities	0.0	0.0
Noncurrent investments, debt securities	0.0	0.0
Other securities, current investments | Carrying Amount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments, debt securities	5.4	9.8
Other securities, current investments | Cost
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments, debt securities	5.4	9.8
Other securities, current investments | Estimate of Fair Value Measurement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments, debt securities	5.4	9.8
Other securities, current investments | Estimate of Fair Value Measurement | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments, debt securities	0.0	0.0
Other securities, current investments | Estimate of Fair Value Measurement | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments, debt securities
Other securities, current investments | Estimate of Fair Value Measurement | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments, debt securities	5.4	9.8
Mortgage-backed securities | Carrying Amount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Noncurrent investments, debt securities	102.5	101.1
Mortgage-backed securities | Cost
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Noncurrent investments, debt securities	99.3	99.6
Mortgage-backed securities | Estimate of Fair Value Measurement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Noncurrent investments, debt securities	102.5	101.1
Mortgage-backed securities | Estimate of Fair Value Measurement | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Noncurrent investments, debt securities	0.0	0.0
Mortgage-backed securities | Estimate of Fair Value Measurement | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Noncurrent investments, debt securities	102.5	101.1
Mortgage-backed securities | Estimate of Fair Value Measurement | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Noncurrent investments, debt securities	0.0	0.0
Other securities, noncurrent investments | Carrying Amount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	60.0	60.0
Other securities, noncurrent investments | Cost
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	27.4	27.4
Other securities, noncurrent investments | Estimate of Fair Value Measurement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	60.2	60.0
Other securities, noncurrent investments | Estimate of Fair Value Measurement | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	0.0	0.0
Other securities, noncurrent investments | Estimate of Fair Value Measurement | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	0.0	0.0
Other securities, noncurrent investments | Estimate of Fair Value Measurement | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	60.2	60.0
Marketable equity securities | Carrying Amount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	869.5	718.6
Marketable equity securities | Cost
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	250.1	254.4
Marketable equity securities | Estimate of Fair Value Measurement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	869.5	718.6
Marketable equity securities | Estimate of Fair Value Measurement | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	869.5	718.6
Marketable equity securities | Estimate of Fair Value Measurement | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	0.0	0.0
Marketable equity securities | Estimate of Fair Value Measurement | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	0.0	0.0
Equity method investments | Carrying Amount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity method investments	$ 348.5	$ 299.4