Financial Instruments (Tables)

12 Months Ended

Dec. 31, 2013

Investments, All Other Investments [Abstract]

Marketable securities including strategic investments

As of December 31, 2013 (In millions)	Fair Value		Gross Unrealized Gains		Gross Unrealized Losses			Amortized Cost
Available-for-sale:
Corporate debt securities
Current	$	100.7	$	—	$	—		$	100.7
Non-current	339.1		0.4		(0.1		)	338.8
Government securities
Current	519.5		—		—			519.5
Non-current	155.2		—		(0.1		)	155.3
Mortgage and other asset backed securities
Current	—		—		—			—
Non-current	131.4		—		(0.1		)	131.5
Total marketable debt securities	$	1,245.9	$	0.4	$	(0.3	)	$	1,245.8
Marketable equity securities, non-current	$	11.2	$	8.7	$	—		$	2.5

As of December 31, 2012 (In millions)	Fair Value		Gross Unrealized Gains		Gross Unrealized Losses			Amortized Cost
Available-for-sale:
Corporate debt securities
Current	$	346.9	$	0.3	$	—		$	346.6
Non-current	654.1		2.8		(0.6		)	651.9
Government securities
Current	783.4		0.3		—			783.1
Non-current	874.4		0.8		—			873.6
Mortgage and other asset backed securities
Current	4.8		—		—			4.8
Non-current	508.1		1.4		(1.3		)	508.0
Total marketable debt securities	$	3,171.7	$	5.6	$	(1.9	)	$	3,168.0
Marketable equity securities, non-current	$	9.0	$	3.0	$	—		$	6.0

Summary of financial assets with maturities of less than 90 days included within cash and cash equivalents

	As of December 31,
(In millions)	2013		2012
Commercial paper	$	1.2	$	40.7
Overnight reverse repurchase agreements	22.4		67.4
Short-term debt securities	401.1		331.3
Total	$	424.7	$	439.4

Summary of contractual maturities: Available-for-sale securities

	As of December 31, 2013				As of December 31, 2012
(In millions)	Estimated Fair  Value		Amortized Cost		Estimated Fair  Value		Amortized Cost
Due in one year or less	$	620.2	$	620.2	$	1,135.0	$	1,134.5
Due after one year through five years	573.1		572.9		1,744.3		1,741.2
Due after five years	52.6		52.7		292.4		292.3
Total available-for-sale securities	$	1,245.9	$	1,245.8	$	3,171.7	$	3,168.0

Proceeds from marketable securities, excluding strategic investments

	For the Years Ended December 31,
(In millions)	2013		2012		2011
Proceeds from maturities and sales	$	5,190.1	$	2,749.6	$	2,276.7
Realized gains	$	6.6	$	2.1	$	3.9
Realized losses	$	2.1	$	3.5	$	2.3