Financial Instruments (Fair Value Measurement) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Noncurrent investments:
Change on the fair value of contingent consideration	$ 203.9	$ 231.0
Portion at Other than Fair Value Measurement [Member]
Statement [Line Items]
Cash equivalents	4,763.9	2,986.8
Carrying Amount
Statement [Line Items]
Cash equivalents	4,763.9	2,986.8
Short-term investments:
Short-term investments	1,497.9	1,456.5
Noncurrent investments:
Available-for-sale Securities, Noncurrent, Total	5,678.8	5,207.5
Other current liabilities	(208.0)	(215.9)
Other noncurrent liabilities	(45.2)	(242.6)
Fair Value
Statement [Line Items]
Cash equivalents	4,763.9	2,986.8
Noncurrent investments:
Other current liabilities	(208.0)	(215.9)
Other noncurrent liabilities	(45.2)	(242.6)
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value
Statement [Line Items]
Cash equivalents	4,712.4	2,699.4
Noncurrent investments:
Other current liabilities	0.0	0.0
Other noncurrent liabilities	0.0	0.0
Significant Other Observable Inputs (Level 2) | Fair Value
Statement [Line Items]
Cash equivalents	51.5	287.4
Noncurrent investments:
Other current liabilities	0.0	0.0
Other noncurrent liabilities	0.0	0.0
Significant Unobservable Inputs (Level 3) | Fair Value
Statement [Line Items]
Cash equivalents	0.0	0.0
Noncurrent investments:
Other current liabilities	(208.0)	(215.9)
Other noncurrent liabilities	(45.2)	(242.6)
U.S. government and agency securities | Portion at Other than Fair Value Measurement [Member]
Short-term investments:
Short-term investments, debt securities	218.2	232.6
Noncurrent investments:
Noncurrent investments, debt securities	365.0	323.8
U.S. government and agency securities | Carrying Amount
Short-term investments:
Short-term investments, debt securities	217.8	232.5
Noncurrent investments:
Noncurrent investments, debt securities	360.0	318.9
U.S. government and agency securities | Fair Value
Short-term investments:
Short-term investments, debt securities	217.8	232.5
Noncurrent investments:
Noncurrent investments, debt securities	360.0	318.9
U.S. government and agency securities | Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value
Short-term investments:
Short-term investments, debt securities	217.8	232.5
Noncurrent investments:
Noncurrent investments, debt securities	360.0	318.9
U.S. government and agency securities | Significant Other Observable Inputs (Level 2) | Fair Value
Short-term investments:
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 | Significant Unobservable Inputs (Level 3) | Fair Value
Short-term investments:
Short-term investments, debt securities	0.0	0.0
Noncurrent investments:
Noncurrent investments, debt securities	0.0	0.0
Corporate debt securities | Portion at Other than Fair Value Measurement [Member]
Short-term investments:
Short-term investments, debt securities	1,183.2	1,219.1
Noncurrent investments:
Noncurrent investments, debt securities	3,473.5	3,074.3
Corporate debt securities | Carrying Amount
Short-term investments:
Short-term investments, debt securities	1,182.3	1,219.2
Noncurrent investments:
Noncurrent investments, debt securities	3,464.3	3,062.2
Corporate debt securities | Fair Value
Short-term investments:
Short-term investments, debt securities	1,182.3	1,219.2
Noncurrent investments:
Noncurrent investments, debt securities	3,464.3	3,062.2
Corporate debt securities | Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value
Short-term investments:
Short-term investments, debt securities	0.0	0.0
Noncurrent investments:
Noncurrent investments, debt securities	0.0	0.0
Corporate debt securities | Significant Other Observable Inputs (Level 2) | Fair Value
Short-term investments:
Short-term investments, debt securities	1,182.3	1,219.2
Noncurrent investments:
Noncurrent investments, debt securities	3,464.3	3,062.2
Corporate debt securities | Significant Unobservable Inputs (Level 3) | Fair Value
Short-term investments:
Short-term investments, debt securities	0.0	0.0
Noncurrent investments:
Noncurrent investments, debt securities	0.0	0.0
Other securities | Portion at Other than Fair Value Measurement [Member]
Short-term investments:
Short-term investments, debt securities	3.6	0.5
Noncurrent investments:
Noncurrent investments, debt securities	66.4	77.6
Other securities | Carrying Amount
Short-term investments:
Short-term investments, debt securities	3.6	0.5
Noncurrent investments:
Noncurrent investments, debt securities	132.1	153.7
Other securities | Fair Value
Short-term investments:
Short-term investments, debt securities	3.6	0.5
Noncurrent investments:
Noncurrent investments, debt securities	132.1	153.7
Other securities | Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value
Short-term investments:
Short-term investments, debt securities	0.0	0.0
Noncurrent investments:
Noncurrent investments, debt securities	0.0	0.0
Other securities | Significant Other Observable Inputs (Level 2) | Fair Value
Short-term investments:
Short-term investments, debt securities	3.6	0.5
Noncurrent investments:
Noncurrent investments, debt securities	0.0	0.0
Other securities | Significant Unobservable Inputs (Level 3) | Fair Value
Short-term investments:
Short-term investments, debt securities	0.0	0.0
Noncurrent investments:
Noncurrent investments, debt securities	132.1	153.7
Mortgage-backed securities | Portion at Other than Fair Value Measurement [Member]
Noncurrent investments:
Noncurrent investments, debt securities	204.2	185.4
Mortgage-backed securities | Carrying Amount
Noncurrent investments:
Noncurrent investments, debt securities	202.4	183.1
Mortgage-backed securities | Fair Value
Noncurrent investments:
Noncurrent investments, debt securities	202.4	183.1
Mortgage-backed securities | Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value
Noncurrent investments:
Noncurrent investments, debt securities	0.0	0.0
Mortgage-backed securities | Significant Other Observable Inputs (Level 2) | Fair Value
Noncurrent investments:
Noncurrent investments, debt securities	202.4	183.1
Mortgage-backed securities | Significant Unobservable Inputs (Level 3) | Fair Value
Noncurrent investments:
Noncurrent investments, debt securities	0.0	0.0
Asset-backed securities | Portion at Other than Fair Value Measurement [Member]
Short-term investments:
Short-term investments, debt securities	94.3	4.3
Noncurrent investments:
Noncurrent investments, debt securities	656.0	503.5
Asset-backed securities | Carrying Amount
Short-term investments:
Short-term investments, debt securities	94.2	4.3
Noncurrent investments:
Noncurrent investments, debt securities	653.9	502.7
Asset-backed securities | Fair Value
Short-term investments:
Short-term investments, debt securities	94.2	4.3
Noncurrent investments:
Noncurrent investments, debt securities	653.9	502.7
Asset-backed securities | Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value
Short-term investments:
Short-term investments, debt securities	0.0	0.0
Noncurrent investments:
Noncurrent investments, debt securities	0.0	0.0
Asset-backed securities | Significant Other Observable Inputs (Level 2) | Fair Value
Short-term investments:
Short-term investments, debt securities	94.2	4.3
Noncurrent investments:
Noncurrent investments, debt securities	653.9	502.7
Asset-backed securities | Significant Unobservable Inputs (Level 3) | Fair Value
Short-term investments:
Short-term investments, debt securities	0.0	0.0
Noncurrent investments:
Noncurrent investments, debt securities	0.0	0.0
Marketable equity securities | Portion at Other than Fair Value Measurement [Member]
Noncurrent investments:
Marketable equity securities	131.0	91.9
Marketable equity securities | Carrying Amount
Noncurrent investments:
Marketable equity securities	281.3	418.2
Marketable equity securities | Fair Value
Noncurrent investments:
Marketable equity securities	281.3	418.2
Marketable equity securities | Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value
Noncurrent investments:
Marketable equity securities	281.3	418.2
Marketable equity securities | Significant Other Observable Inputs (Level 2) | Fair Value
Noncurrent investments:
Marketable equity securities	0.0	0.0
Marketable equity securities | Significant Unobservable Inputs (Level 3) | Fair Value
Noncurrent investments:
Marketable equity securities	0.0	0.0
Cost and equity method investments | Carrying Amount
Noncurrent investments:
Cost and equity method investments	584.8	568.7
Designated as Hedging Instrument | Cross-currency interest rate swaps | Carrying Amount
Noncurrent investments:
Sundry		31.4
Other current liabilities	(33.4)
Other noncurrent liabilities	(26.0)
Designated as Hedging Instrument | Cross-currency interest rate swaps | Fair Value
Noncurrent investments:
Sundry		31.4
Other current liabilities	(33.4)
Other noncurrent liabilities	(26.0)
Designated as Hedging Instrument | Cross-currency interest rate swaps | Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value
Noncurrent investments:
Sundry		0.0
Other current liabilities	0.0
Other noncurrent liabilities	0.0
Designated as Hedging Instrument | Cross-currency interest rate swaps | Significant Other Observable Inputs (Level 2) | Fair Value
Noncurrent investments:
Sundry		31.4
Other current liabilities	(33.4)
Other noncurrent liabilities	(26.0)
Designated as Hedging Instrument | Cross-currency interest rate swaps | Significant Unobservable Inputs (Level 3) | Fair Value
Noncurrent investments:
Sundry		0.0
Other current liabilities	0.0
Other noncurrent liabilities	0.0
Designated as Hedging Instrument | Interest Rate Contract | Carrying Amount
Noncurrent investments:
Other receivables	0.8	2.4
Sundry	35.1	37.0
Other current liabilities	(0.2)
Other noncurrent liabilities	(10.5)	(0.5)
Designated as Hedging Instrument | Interest Rate Contract | Fair Value
Noncurrent investments:
Other receivables	0.8	2.4
Sundry	35.1	37.0
Other current liabilities	(0.2)
Other noncurrent liabilities	(10.5)	(0.5)
Designated as Hedging Instrument | Interest Rate Contract | Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value
Noncurrent investments:
Other receivables	0.0	0.0
Sundry	0.0	0.0
Other current liabilities	0.0
Other noncurrent liabilities	0.0	0.0
Designated as Hedging Instrument | Interest Rate Contract | Significant Other Observable Inputs (Level 2) | Fair Value
Noncurrent investments:
Other receivables	0.8	2.4
Sundry	35.1	37.0
Other current liabilities	(0.2)
Other noncurrent liabilities	(10.5)	(0.5)
Designated as Hedging Instrument | Interest Rate Contract | Significant Unobservable Inputs (Level 3) | Fair Value
Noncurrent investments:
Other receivables	0.0	0.0
Sundry	0.0	0.0
Other current liabilities	0.0
Other noncurrent liabilities	0.0	0.0
Not Designated as Hedging Instrument | Foreign Exchange Contract | Carrying Amount
Noncurrent investments:
Other receivables	26.8	31.8
Other current liabilities	(36.0)	(21.7)
Not Designated as Hedging Instrument | Foreign Exchange Contract | Fair Value
Noncurrent investments:
Other receivables	26.8	31.8
Other current liabilities	(36.0)	(21.7)
Not Designated as Hedging Instrument | Foreign Exchange Contract | Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value
Noncurrent investments:
Other receivables	0.0	0.0
Other current liabilities	0.0	0.0
Not Designated as Hedging Instrument | Foreign Exchange Contract | Significant Other Observable Inputs (Level 2) | Fair Value
Noncurrent investments:
Other receivables	26.8	31.8
Other current liabilities	(36.0)	(21.7)
Not Designated as Hedging Instrument | Foreign Exchange Contract | Significant Unobservable Inputs (Level 3) | Fair Value
Noncurrent investments:
Other receivables	0.0	0.0
Other current liabilities	$ 0.0	$ 0.0