CASH, CASH EQUIVALENTS AND MARKETABLE SECURITIES

Components for cash, cash equivalents and marketable securities (in millions):



December 31, 2011	Cost Basis		Unrealized Gains		Unrealized Losses			Fair Value
Cash	$	62.1	$	—	$	—		$	62.1
Money market funds	40.1		—		—			40.1
Cash and cash equivalents	102.2		—		—			102.2
U.S. government and agency securities	292.5		3.4		—			295.9
Foreign government bonds	24.9		0.5		—			25.4
Asset-back securities	58.2		0.1		(0.3		)	58.0
Mortgage-back securities	124.1		1.1		(0.3		)	124.9
Corporate notes and bonds	518.0		7.0		(2.4		)	522.6
Municipal securities	11.8		0.1		—			11.9
Marketable securities	1,029.5		12.2		(3.0		)	1,038.7
Total	$	1,131.7	$	12.2	$	(3.0	)	$	1,140.9



December 31, 2010	Cost Basis		Unrealized Gains		Unrealized Losses			Fair Value
Cash	$	6.6	$	—	$	—		$	6.6
Money market funds	82.9		—		—			82.9
Cash and cash equivalents	89.5		—		—			89.5
U.S. government and agency securities	469.8		4.3		(1.2		)	472.9
Foreign government bonds	41.0		0.8		(0.2		)	41.6
Asset-back securities	51.7		0.3		(0.3		)	51.7
Mortgage-back securities	125.7		1.0		(1.2		)	125.5
Corporate notes and bonds	411.1		9.7		(0.5		)	420.3
Municipal securities	6.5		0.2		—			6.7
Marketable securities	1,105.8		16.3		(3.4		)	1,118.7
Total	$	1,195.3	$	16.3	$	(3.4	)	$	1,208.2

Activity for marketable securities for the years ended December 31 (in millions):



	2011		2010		2009
Proceeds from sales and maturities	$	955.7	$	931.0	$	725.0
Gross realized gains	7.5		10.4		7.0
Gross realized losses	2.3		2.3		2.3
Other-than-temporarily impairments on investments	2.2		—		2.2

Of the marketable securities on hand at December 31, 2011, 23.4% mature in 2012, 35.8% in 2013, and 40.8% thereafter.

Investments with continuous unrealized losses (in millions):



	Less than 12 months					Greater than 12 months
December 31, 2011	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses			Total Fair Value		Total Unrealized Losses
Asset-backed obligations	$	31.7	$	(0.1	)	$	1.1	$	(0.2	)	$	32.8	$	(0.3	)
Mortgage-backed obligations	35.1		(0.2		)	1.9		(0.1		)	37.0		(0.3		)
Corporate notes and bonds	137.4		(2.4		)	1.0		—			138.4		(2.4		)
Total	$	204.2	$	(2.7	)	$	4.0	$	(0.3	)	$	208.2	$	(3.0	)



	Less than 12 months					Greater than 12 months
December 31, 2010	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses			Total Fair Value		Total Unrealized Losses
U.S. government and agency securities	$	163.3	$	(1.2	)	$	—	$	—		$	163.3	$	(1.2	)
Foreign government bonds	—		—			41.6		(0.2		)	41.6		(0.2		)
Asset-backed obligations	15.6		(0.1		)	1.9		(0.2		)	17.5		(0.3		)
Mortgage-backed obligations	51.4		(0.4		)	8.8		(0.8		)	60.2		(1.2		)
Corporate notes and bonds	60.6		(0.5		)	1.8		—			62.4		(0.5		)
Total	$	290.9	$	(2.2	)	$	54.1	$	(1.2	)	$	345.0	$	(3.4	)

Unrealized losses from fixed-income securities are primarily attributable to changes in interest rates. Management does not believe any remaining unrealized losses represent other-than-temporary impairments based on our evaluation of available evidence as of December 31, 2011.