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2. Short-term Investments (Details) (Fair Value, Measurements, Recurring [Member], USD $)
In Millions
Sep. 30, 2011
Dec. 31, 2010
Schedule of Available-for-sale Securities [Line Items]  
Amortized Cost$ 296.5$ 163.6
Unrealized Gains55.249.3
Unrealized Losses(2.6)(1.1)
Estimated Fair Value349.1211.8
Corporate Debt Securities [Member] | Short-term Investments [Member]
  
Schedule of Available-for-sale Securities [Line Items]  
Amortized Cost194.339.8
Unrealized Gains00
Unrealized Losses(0.4)0
Estimated Fair Value193.939.8
Certificates of Deposit [Member] | Short-term Investments [Member]
  
Schedule of Available-for-sale Securities [Line Items]  
Amortized Cost6.8 
Unrealized Gains0 
Unrealized Losses0 
Estimated Fair Value6.8 
US Government Agencies Debt Securities [Member] | Short-term Investments [Member]
  
Schedule of Available-for-sale Securities [Line Items]  
Amortized Cost18.054.7
Unrealized Gains00
Unrealized Losses00
Estimated Fair Value18.054.7
Foreign Government Debt Securities [Member] | Long Term Investments [Member]
  
Schedule of Available-for-sale Securities [Line Items]  
Amortized Cost0.9 
Unrealized Gains0 
Unrealized Losses0 
Estimated Fair Value0.9 
Foreign Government Debt Securities [Member] | Short-term Investments [Member]
  
Schedule of Available-for-sale Securities [Line Items]  
Amortized Cost5.44.5
Unrealized Gains00
Unrealized Losses00
Estimated Fair Value5.44.5
Municipal Bonds [Member] | Short-term Investments [Member]
  
Schedule of Available-for-sale Securities [Line Items]  
Amortized Cost5.07.7
Unrealized Gains00
Unrealized Losses00
Estimated Fair Value5.07.7
Equity Securities [Member] | Long Term Investments [Member]
  
Schedule of Available-for-sale Securities [Line Items]  
Amortized Cost55.345.5
Unrealized Gains54.847.9
Unrealized Losses(1.5)(0.9)
Estimated Fair Value108.692.5
Equity Securities [Member] | Short-term Investments [Member]
  
Schedule of Available-for-sale Securities [Line Items]  
Amortized Cost8.08.8
Unrealized Gains0.41.3
Unrealized Losses(0.6)(0.1)
Estimated Fair Value7.810.0
Asset-backed Securities [Member] | Long Term Investments [Member]
  
Schedule of Available-for-sale Securities [Line Items]  
Amortized Cost0.50.7
Unrealized Gains00.1
Unrealized Losses(0.1)(0.1)
Estimated Fair Value0.40.7
Asset-backed Securities [Member] | Short-term Investments [Member]
  
Schedule of Available-for-sale Securities [Line Items]  
Amortized Cost2.31.9
Unrealized Gains00
Unrealized Losses00
Estimated Fair Value2.31.9
Long Term Investments [Member] | Available-for-sale Securities [Member]
  
Schedule of Available-for-sale Securities [Line Items]  
Amortized Cost56.746.2
Unrealized Gains54.848.0
Unrealized Losses(1.6)(1.0)
Estimated Fair Value109.993.2
Short-term Investments [Member] | Available-for-sale Securities [Member]
  
Schedule of Available-for-sale Securities [Line Items]  
Amortized Cost239.8117.4
Unrealized Gains0.41.3
Unrealized Losses(1.0)(0.1)
Estimated Fair Value$ 239.2$ 118.6