Fair Value Measurements (Details) (USD $)	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2011	Dec. 31, 2010
Liabilities:
Contingent consideration	$ 269,900,000	$ 151,000,000	$ 82,400,000	$ 81,200,000
Fair Value, Measurements, Recurring [Member]
Assets:
Cash equivalents	161,400,000	399,800,000
Derivative contracts	16,900,000	39,500,000
Plan assets for deferred compensation	12,600,000	11,600,000
Total	2,663,500,000	3,067,400,000
Liabilities:
Derivative contracts	900,000	500,000
Contingent consideration	269,900,000	151,000,000
Total	270,800,000	151,500,000
Fair Value, Measurements, Recurring [Member] | Corporate debt securities [Member]
Assets:
Fair Value, Measured on Recurring Basis, Investments	725,900,000	602,600,000
Fair Value, Measurements, Recurring [Member] | Government securities [Member]
Assets:
Fair Value, Measured on Recurring Basis, Investments	1,368,600,000	1,716,500,000
Fair Value, Measurements, Recurring [Member] | Mortgage and other asset backed securities [Member]
Assets:
Fair Value, Measured on Recurring Basis, Investments	355,900,000	273,800,000
Fair Value, Measurements, Recurring [Member] | Marketable equity securities [Member]
Assets:
Fair Value, Measured on Recurring Basis, Investments	100,000	100,000
Fair Value, Measurements, Recurring [Member] | Venture capital investments [Member]
Assets:
Fair Value, Measured on Recurring Basis, Investments	22,100,000	23,500,000
Quoted Prices in Active Markets, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Total	100,000	100,000
Quoted Prices in Active Markets, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Marketable equity securities [Member]
Assets:
Fair Value, Measured on Recurring Basis, Investments	100,000	100,000
Significant Other Observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Cash equivalents	161,400,000	399,800,000
Derivative contracts	16,900,000	39,500,000
Plan assets for deferred compensation	12,600,000	11,600,000
Total	2,641,300,000	3,043,800,000
Liabilities:
Derivative contracts	900,000	500,000
Total	900,000	500,000
Significant Other Observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member] | Corporate debt securities [Member]
Assets:
Fair Value, Measured on Recurring Basis, Investments	725,900,000	602,600,000
Significant Other Observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member] | Government securities [Member]
Assets:
Fair Value, Measured on Recurring Basis, Investments	1,368,600,000	1,716,500,000
Significant Other Observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member] | Mortgage and other asset backed securities [Member]
Assets:
Fair Value, Measured on Recurring Basis, Investments	355,900,000	273,800,000
Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Total	22,100,000	23,500,000
Liabilities:
Contingent consideration	269,900,000	151,000,000
Total	269,900,000	151,000,000
Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Recurring [Member] | Venture capital investments [Member]
Assets:
Fair Value, Measured on Recurring Basis, Investments	$ 22,100,000	$ 23,500,000