Financial Instruments (Tables)

12 Months Ended

Dec. 31, 2012

Investments, All Other Investments [Abstract]

Marketable securities including strategic investments

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

As of December 31, 2011 (In millions)	Fair Value		Gross Unrealized Gains		Gross Unrealized Losses			Amortized Cost
Available-for-sale:
Corporate debt securities
Current	$	155.0	$	0.2	$	(0.1	)	$	154.9
Non-current	447.6		1.2		(1.5		)	447.9
Government securities
Current	1,021.0		0.4		—			1,020.6
Non-current	695.5		0.9		(0.2		)	694.8
Mortgage and other asset backed securities
Current	0.1		—		—			0.1
Non-current	273.7		0.5		(1.3		)	274.5
Total marketable debt securities	$	2,592.9	$	3.2	$	(3.1	)	$	2,592.8
Marketable equity securities, non-current	$	0.1	$	—	$	(0.1	)	$	0.2

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

	As of December 31,
(In millions)	2012		2011
Commercial paper	$	40.7	$	—
Repurchase agreements	67.4		8.8
Short-term debt securities	331.3		391.0
Total	$	439.4	$	399.8

Summary of contractual maturities: Available-for-sale securities

	As of December 31, 2012				As of December 31, 2011
(In millions)	Estimated Fair  Value		Amortized Cost		Estimated Fair  Value		Amortized Cost
Due in one year or less	$	1,135.0	$	1,134.5	$	1,176.1	$	1,175.6
Due after one year through five years	1,744.3		1,741.2		1,251.6		1,251.4
Due after five years	292.4		292.3		165.2		165.8
Total available-for-sale securities	$	3,171.7	$	3,168.0	$	2,592.9	$	2,592.8

Proceeds from marketable securities, excluding strategic investments

	For the Years Ended December 31,
(In millions)	2012		2011		2010
Proceeds from maturities and sales	$	2,749.6	$	2,276.7	$	2,668.7
Realized gains	$	2.1	$	3.9	$	18.8
Realized losses	$	3.5	$	2.3	$	2.5