3. Fair Value Measurements (Details) - Fair Value, Measurements, Recurring [Member] - USD ($) $ in Millions		Dec. 31, 2016		Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Restricted Investments, at Fair Value		$ 4.6		$ 4.2
Available-for-sale investments	[1]	1,115.6		957.6
Forward foreign exchange contracts, Asset	[2]	0.6		0.9
Financial Assets Carried at Fair Value		1,173.7		1,034.3
Forward foreign exchange contracts, Liability	[3]	1.3		1.1
Business Combination, Contingent Consideration, Liability	[4]	38.5		19.1
Liabilities, Fair Value Disclosure		39.8		20.2
Interest-bearing Deposits [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments		3.6
Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	[1]	179.4		156.9
US Government Sponsored Agencies [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	[1]	82.5		74.8
Foreign Government Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	[1]	4.4		4.6
Municipal Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	[1]	15.4		6.4
Marketable Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	[1]	767.8		660.1
Asset-backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	[1]	62.5		54.8
Foreign Government Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents				0.6
Foreign Time Deposits [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	[5]	11.8		11.9
US Government Sponsored Agencies [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents		1.1	[5]	14.6
Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	[5]	5.9		11.3
Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	[5]	14.1		33.2
Cash Equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	[5]	52.9		71.6
Domestic Time Deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents		20.0
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Restricted Investments, at Fair Value		4.6		4.2
Available-for-sale investments	[1]	767.8		660.1
Forward foreign exchange contracts, Asset	[2]	0.0		0.0
Financial Assets Carried at Fair Value		790.1		687.5
Forward foreign exchange contracts, Liability	[3]	0.0		0.0
Business Combination, Contingent Consideration, Liability	[4]	0.0		0.0
Liabilities, Fair Value Disclosure		0.0		0.0
Fair Value, Inputs, Level 1 [Member] | Interest-bearing Deposits [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments		0.0
Fair Value, Inputs, Level 1 [Member] | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	[1]	0.0		0.0
Fair Value, Inputs, Level 1 [Member] | US Government Sponsored Agencies [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	[1]	0.0		0.0
Fair Value, Inputs, Level 1 [Member] | Foreign Government Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	[1]	0.0		0.0
Fair Value, Inputs, Level 1 [Member] | Municipal Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	[1]	0.0		0.0
Fair Value, Inputs, Level 1 [Member] | Marketable Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	[1]	767.8		660.1
Fair Value, Inputs, Level 1 [Member] | Asset-backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	[1]	0.0		0.0
Fair Value, Inputs, Level 1 [Member] | Foreign Government Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents				0.0
Fair Value, Inputs, Level 1 [Member] | Foreign Time Deposits [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	[5]	11.8		11.9
Fair Value, Inputs, Level 1 [Member] | US Government Sponsored Agencies [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents		0.0	[5]	0.0
Fair Value, Inputs, Level 1 [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	[5]	5.9		11.3
Fair Value, Inputs, Level 1 [Member] | Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	[5]	0.0		0.0
Fair Value, Inputs, Level 1 [Member] | Cash Equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	[5]	17.7		23.2
Fair Value, Inputs, Level 1 [Member] | Domestic Time Deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents		0.0
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Restricted Investments, at Fair Value		0.0		0.0
Available-for-sale investments	[1]	347.8		297.5
Forward foreign exchange contracts, Asset	[2]	0.6		0.9
Financial Assets Carried at Fair Value		383.6		346.8
Forward foreign exchange contracts, Liability	[3]	1.3		1.1
Business Combination, Contingent Consideration, Liability	[4]	0.0		0.0
Liabilities, Fair Value Disclosure		1.3		1.1
Fair Value, Inputs, Level 2 [Member] | Interest-bearing Deposits [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments		3.6
Fair Value, Inputs, Level 2 [Member] | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	[1]	179.4		156.9
Fair Value, Inputs, Level 2 [Member] | US Government Sponsored Agencies [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	[1]	82.5		74.8
Fair Value, Inputs, Level 2 [Member] | Foreign Government Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	[1]	4.4		4.6
Fair Value, Inputs, Level 2 [Member] | Municipal Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	[1]	15.4		6.4
Fair Value, Inputs, Level 2 [Member] | Marketable Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	[1]	0.0		0.0
Fair Value, Inputs, Level 2 [Member] | Asset-backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	[1]	62.5		54.8
Fair Value, Inputs, Level 2 [Member] | Foreign Government Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents				0.6
Fair Value, Inputs, Level 2 [Member] | Foreign Time Deposits [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	[5]	0.0		0.0
Fair Value, Inputs, Level 2 [Member] | US Government Sponsored Agencies [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents		1.1	[5]	14.6
Fair Value, Inputs, Level 2 [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	[5]	0.0		0.0
Fair Value, Inputs, Level 2 [Member] | Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	[5]	14.1		33.2
Fair Value, Inputs, Level 2 [Member] | Cash Equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	[5]	35.2		48.4
Fair Value, Inputs, Level 2 [Member] | Domestic Time Deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents		20.0
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Restricted Investments, at Fair Value		0.0		0.0
Available-for-sale investments	[1]	0.0		0.0
Forward foreign exchange contracts, Asset	[2]	0.0		0.0
Financial Assets Carried at Fair Value		0.0		0.0
Forward foreign exchange contracts, Liability	[3]	0.0		0.0
Business Combination, Contingent Consideration, Liability	[4]	38.5		19.1
Liabilities, Fair Value Disclosure		38.5		19.1
Fair Value, Inputs, Level 3 [Member] | Interest-bearing Deposits [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments		0.0
Fair Value, Inputs, Level 3 [Member] | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	[1]	0.0		0.0
Fair Value, Inputs, Level 3 [Member] | US Government Sponsored Agencies [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	[1]	0.0		0.0
Fair Value, Inputs, Level 3 [Member] | Foreign Government Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	[1]	0.0		0.0
Fair Value, Inputs, Level 3 [Member] | Municipal Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	[1]	0.0		0.0
Fair Value, Inputs, Level 3 [Member] | Marketable Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	[1]	0.0		0.0
Fair Value, Inputs, Level 3 [Member] | Asset-backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	[1]	0.0		0.0
Fair Value, Inputs, Level 3 [Member] | Foreign Government Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents				0.0
Fair Value, Inputs, Level 3 [Member] | Foreign Time Deposits [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	[5]	0.0		0.0
Fair Value, Inputs, Level 3 [Member] | US Government Sponsored Agencies [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents		0.0	[5]	0.0
Fair Value, Inputs, Level 3 [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	[5]	0.0		0.0
Fair Value, Inputs, Level 3 [Member] | Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	[5]	0.0		0.0
Fair Value, Inputs, Level 3 [Member] | Cash Equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	[5]	0.0		0.0
Fair Value, Inputs, Level 3 [Member] | Domestic Time Deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents		0.0
Other Current Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Business Combination, Contingent Consideration, Liability		14.5		13.5
Short-term Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments		383.2		328.7
Short-term Investments [Member] | Interest-bearing Deposits [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments		3.6
Short-term Investments [Member] | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments		179.4		156.9
Short-term Investments [Member] | US Government Sponsored Agencies [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments		82.5		74.8
Short-term Investments [Member] | Foreign Government Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments		4.4		4.6
Short-term Investments [Member] | Municipal Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments		15.4		6.4
Short-term Investments [Member] | Marketable Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments		35.7		31.4
Short-term Investments [Member] | Asset-backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments		62.2		54.6
Other Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments		732.4		628.9
Other Noncurrent Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Business Combination, Contingent Consideration, Liability		$ 24.0		$ 5.6

[1] Available-for-sale investments are included in the following accounts in the Consolidated Balance Sheets (in millions):   December 31,
2016   December 31, 2015         Short-term investments $ 383.2
  $ 328.7
Other investments 732.4
  628.9
Total $ 1,115.6
  $ 957.6

[2] Forward foreign exchange contracts in an asset position are included in Other current assets in the Consolidated Balance Sheets.

[3] Forward foreign exchange contracts in a liability position are included in Other current liabilities in the Consolidated Balance Sheets.

[4] Contingent consideration liabilities are included in the following accounts in the Consolidated Balance Sheets (in millions):   December 31, 2016   December 31, 2015         Other current liabilities $ 14.5
  $ 13.5
Other long-term liabilities 24.0
  5.6
   Total $ 38.5
  $ 19.1

[5] Cash equivalents are included in Cash and cash equivalents in the Consolidated Balance Sheets.