Fair Value Measurements (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011
Assets:
Marketable debt securities	$ 382.3		$ 3,171.7
Fair Value, Measurements, Recurring [Member]
Assets:
Cash equivalents	261.5		439.4
Derivative contracts	5.9		1.8
Plan assets for deferred compensation	16.1		14.3
Total	718.2		3,656.5
Liabilities:
Derivative contracts	5.9		14.4
Contingent consideration obligations	281.0	293.7	293.9	280.9	269.9	151.0
Total	286.9		308.3
Fair Value, Measurements, Recurring [Member] | Corporate debt securities [Member]
Assets:
Marketable debt securities	99.6		1,001.0
Fair Value, Measurements, Recurring [Member] | Government securities [Member]
Assets:
Marketable debt securities	273.2		1,657.8
Fair Value, Measurements, Recurring [Member] | Mortgage and other asset backed securities [Member]
Assets:
Marketable debt securities	9.5		512.9
Fair Value, Measurements, Recurring [Member] | Marketable equity securities [Member]
Assets:
Investments	28.9		9.0
Fair Value, Measurements, Recurring [Member] | Venture capital investments [Member]
Assets:
Investments	23.5	18.0	20.3	25.4	22.1	23.5
Quoted Prices in Active Markets, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Cash equivalents	0		0
Derivative contracts	0		0
Plan assets for deferred compensation	0		0
Total	28.9		9.0
Liabilities:
Derivative contracts	0		0
Contingent consideration obligations	0		0
Total	0		0
Quoted Prices in Active Markets, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Corporate debt securities [Member]
Assets:
Marketable debt securities	0		0
Quoted Prices in Active Markets, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Government securities [Member]
Assets:
Marketable debt securities	0		0
Quoted Prices in Active Markets, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Mortgage and other asset backed securities [Member]
Assets:
Marketable debt securities	0		0
Quoted Prices in Active Markets, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Marketable equity securities [Member]
Assets:
Investments	28.9		9.0
Quoted Prices in Active Markets, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Venture capital investments [Member]
Assets:
Investments	0		0
Significant Other Observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Cash equivalents	261.5		439.4
Derivative contracts	5.9		1.8
Plan assets for deferred compensation	16.1		14.3
Total	665.8		3,627.2
Liabilities:
Derivative contracts	5.9		14.4
Contingent consideration obligations	0		0
Total	5.9		14.4
Significant Other Observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member] | Corporate debt securities [Member]
Assets:
Marketable debt securities	99.6		1,001.0
Significant Other Observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member] | Government securities [Member]
Assets:
Marketable debt securities	273.2		1,657.8
Significant Other Observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member] | Mortgage and other asset backed securities [Member]
Assets:
Marketable debt securities	9.5		512.9
Significant Other Observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member] | Marketable equity securities [Member]
Assets:
Investments	0		0
Significant Other Observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member] | Venture capital investments [Member]
Assets:
Investments	0		0
Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Cash equivalents	0		0
Derivative contracts	0		0
Plan assets for deferred compensation	0		0
Total	23.5		20.3
Liabilities:
Derivative contracts	0		0
Contingent consideration obligations	281.0		293.9
Total	281.0		293.9
Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Recurring [Member] | Corporate debt securities [Member]
Assets:
Marketable debt securities	0		0
Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Recurring [Member] | Government securities [Member]
Assets:
Marketable debt securities	0		0
Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Recurring [Member] | Mortgage and other asset backed securities [Member]
Assets:
Marketable debt securities	0		0
Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Recurring [Member] | Marketable equity securities [Member]
Assets:
Investments	0		0
Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Recurring [Member] | Venture capital investments [Member]
Assets:
Investments	$ 23.5		$ 20.3