CASH, CASH EQUIVALENTS AND MARKETABLE SECURITIES

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



March 31, 2015	Cost Basis		Unrealized Gains		Unrealized Losses			Fair Value
Cash	$	5	$	—	$	—		$	5
Cash equivalents	46		—		—			46
Cash and cash equivalents	51		—		—			51
U.S. government and agency securities	200		1		—			201
Foreign government bonds	31		—		—			31
Asset-backed securities	151		—		—			151
Mortgage-backed securities	127		1		(1		)	127
Corporate notes and bonds	721		6		—			727
Municipal securities	24		—		—			24
Marketable securities	1,254		8		(1		)	1,261
Total	$	1,305	$	8	$	(1	)	$	1,312



December 31, 2014	Cost Basis		Unrealized Gains		Unrealized Losses			Fair Value
Cash	$	4	$	—	$	—		$	4
Cash equivalents	103		—		—			103
Cash and cash equivalents	107		—		—			107
U.S. government and agency securities	166		—		—			166
Foreign government bonds	25		—		—			25
Asset-backed securities	130		—		—			130
Mortgage-backed securities	127		—		(1		)	126
Corporate notes and bonds	644		3		(2		)	645
Municipal securities	18		—		—			18
Marketable securities	1,110		3		(3		)	1,110
Total	$	1,217	$	3	$	(3	)	$	1,217

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 March 31, 2015.

Activity for marketable securities (in millions):



	Three Months Ended March 31,
	2015			2014
Proceeds from sales and maturities	$	259		$	227
Gross realized gains	1			1
Gross realized losses	(1		)	(1		)

Maturities for marketable securities (in millions):



March 31, 2015	Cost Basis		Fair Value
Due in one year or less	$	152	$	151
Due after one year through five years	1,099		1,106
Due after five years through 10 years	3		4
Due after 10 years	—		—
Total	$	1,254	$	1,261