Fair Value Measurements (Details) - USD ($) $ in Millions	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013
Assets:
Marketable debt securities	$ 3,188.4		$ 2,111.1
Fair Value, Measurements, Recurring
Assets:
Cash equivalents	974.0		716.3
Investments	6.8		6.9
Derivative contracts	100.5		72.7
Plan assets for deferred compensation	40.7		36.9
Total	4,310.4		2,943.9
Liabilities:
Derivative contracts	27.7		5.4
Contingent consideration obligations	495.6	$ 461.8	215.5	$ 279.1	$ 275.1	$ 280.9
Total	523.3		220.9
Fair Value, Measurements, Recurring | Corporate debt securities
Assets:
Marketable debt securities	1,198.1		1,063.0
Fair Value, Measurements, Recurring | Government securities
Assets:
Marketable debt securities	1,700.3		849.8
Fair Value, Measurements, Recurring | Mortgage and other asset backed securities
Assets:
Marketable debt securities	290.0		198.3
Quoted Prices in Active Markets, Level 1 | Fair Value, Measurements, Recurring
Assets:
Cash equivalents	0.0		0.0
Investments	6.8		6.9
Derivative contracts	0.0		0.0
Plan assets for deferred compensation	0.0		0.0
Total	6.8		6.9
Liabilities:
Derivative contracts	0.0		0.0
Contingent consideration obligations	0.0		0.0
Total	0.0		0.0
Quoted Prices in Active Markets, Level 1 | Fair Value, Measurements, Recurring | Corporate debt securities
Assets:
Marketable debt securities	0.0		0.0
Quoted Prices in Active Markets, Level 1 | Fair Value, Measurements, Recurring | Government securities
Assets:
Marketable debt securities	0.0		0.0
Quoted Prices in Active Markets, Level 1 | Fair Value, Measurements, Recurring | Mortgage and other asset backed securities
Assets:
Marketable debt securities	0.0		0.0
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring
Assets:
Cash equivalents	974.0		716.3
Investments	0.0		0.0
Derivative contracts	100.5		72.7
Plan assets for deferred compensation	40.7		36.9
Total	4,303.6		2,937.0
Liabilities:
Derivative contracts	27.7		5.4
Contingent consideration obligations	0.0		0.0
Total	27.7		5.4
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Corporate debt securities
Assets:
Marketable debt securities	1,198.1		1,063.0
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Government securities
Assets:
Marketable debt securities	1,700.3		849.8
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Mortgage and other asset backed securities
Assets:
Marketable debt securities	290.0		198.3
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring
Assets:
Cash equivalents	0.0		0.0
Investments	0.0		0.0
Derivative contracts	0.0		0.0
Plan assets for deferred compensation	0.0		0.0
Total	0.0		0.0
Liabilities:
Derivative contracts	0.0		0.0
Contingent consideration obligations	495.6		215.5
Total	495.6		215.5
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring | Corporate debt securities
Assets:
Marketable debt securities	0.0		0.0
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring | Government securities
Assets:
Marketable debt securities	0.0		0.0
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring | Mortgage and other asset backed securities
Assets:
Marketable debt securities	$ 0.0		$ 0.0