CASH, CASH EQUIVALENTS AND MARKETABLE SECURITIES

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



June 30, 2012	Cost Basis		Unrealized Gains		Unrealized Losses			Fair Value
Cash	$	23.2	$	—	$	—		$	23.2
Commercial paper, money market funds and other securities	12.2		—		—			12.2
Cash and cash equivalents	35.4		—		—			35.4
U.S. government and agency securities	366.0		2.8		—			368.8
Foreign government bonds	41.4		0.9		—			42.3
Asset-back securities	90.3		0.4		—			90.7
Mortgage-back securities	109.6		0.9		(0.1		)	110.4
Corporate notes and bonds	516.8		6.5		(0.5		)	522.8
Municipal securities	14.9		0.1		—			15.0
Marketable securities	1,139.0		11.6		(0.6		)	1,150.0
Total	$	1,174.4	$	11.6	$	(0.6	)	$	1,185.4



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

Activity for marketable securities (in millions):



	Three Months Ended June 30,				Six Months Ended June 30,
	2012		2011		2012		2011
Proceeds from sales and maturities	$	242.3	$	145.0	$	430.4	$	459.0
Gross realized gains	2.0		1.4		3.6		3.3
Gross realized losses	0.5		0.4		0.8		1.7
Other-than-temporary impairments on investments	—		—		0.3		—

Of the marketable securities on hand at June 30, 2012, 9.8% mature in 2012, 29.5% in 2013, and 60.7% thereafter.

Investments with continuous unrealized losses (in millions):



	Less than 12 months					Greater than 12 months
June 30, 2012	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses		Total Fair Value		Total Unrealized Losses
Mortgage-backed obligations	$	26.3	$	(0.1	)	$	—	$	—	$	26.3	$	(0.1	)
Corporate notes and bonds	106.3		(0.5		)	—		—		106.3		(0.5		)
Total	$	132.6	$	(0.6	)	$	—	$	—	$	132.6	$	(0.6	)



	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	)

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 June 30, 2012.