Fair Value Measurements (Details) - USD ($) $ in Millions	Sep. 30, 2015	Jun. 30, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Dec. 31, 2013
Assets:
Marketable debt securities	$ 3,700.9		$ 2,111.1
Fair Value, Measurements, Recurring
Assets:
Cash equivalents	3,804.2		716.3
Investments	25.7		6.9
Derivative contracts	61.4		72.7
Plan assets for deferred compensation	38.6		36.9
Total	7,630.8		2,943.9
Liabilities:
Derivative contracts	31.3		5.4
Contingent consideration obligations	481.4	$ 495.7	215.5	$ 213.2	$ 279.1	$ 280.9
Total	512.7		220.9
Fair Value, Measurements, Recurring | Corporate debt securities
Assets:
Marketable debt securities	1,039.9		1,063.0
Fair Value, Measurements, Recurring | Government securities
Assets:
Marketable debt securities	2,411.1		849.8
Fair Value, Measurements, Recurring | Mortgage and other asset backed securities
Assets:
Marketable debt securities	249.9		198.3
Quoted Prices in Active Markets, Level 1 | Fair Value, Measurements, Recurring
Assets:
Cash equivalents	0.0		0.0
Investments	25.7		6.9
Derivative contracts	0.0		0.0
Plan assets for deferred compensation	0.0		0.0
Total	25.7		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	3,804.2		716.3
Investments	0.0		0.0
Derivative contracts	61.4		72.7
Plan assets for deferred compensation	38.6		36.9
Total	7,605.1		2,937.0
Liabilities:
Derivative contracts	31.3		5.4
Contingent consideration obligations	0.0		0.0
Total	31.3		5.4
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Corporate debt securities
Assets:
Marketable debt securities	1,039.9		1,063.0
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Government securities
Assets:
Marketable debt securities	2,411.1		849.8
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Mortgage and other asset backed securities
Assets:
Marketable debt securities	249.9		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	481.4		215.5
Total	481.4		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