Available-for-sale securities

12 Months Ended

Dec. 31, 2014

Investments, Debt and Equity Securities [Abstract]

Available-for-Sale Securities Disclosure

AVAILABLE-FOR-SALE SECURITIES

Estimated fair values of available-for-sale securities are generally based on prices obtained from commercial pricing services. The following table is a summary of available-for-sale securities recorded in cash and cash equivalents or marketable securities in our Consolidated Balance Sheets (in millions):

	December 31, 2014									December 31, 2013
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value		Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value
Money market funds	$	7,926	$	—	$	—		$	7,926	$	1,491	$	—	$	—	$	1,491
Corporate debt securities	941		—		(3		)	938		219		1		—		220
U.S. treasury securities	363		—		—			363		86		—		—		86
Residential mortgage and asset-backed securities	269		—		—			269		47		—		—		47
U.S. government agencies securities	113		—		—			113		93		—		—		93
Municipal debt securities	16		—		—			16		12		—		—		12
Total	$	9,628	$	—	$	(3	)	$	9,625	$	1,948	$	1	$	—	$	1,949

The following table summarizes the classification of the available-for-sale securities on our Consolidated Balance Sheets (in millions):

	December 31, 2014		December 31, 2013
Cash and cash equivalents	$	7,926	$	1,491
Short-term marketable securities	101		19
Long-term marketable securities	1,598		439
Total	$	9,625	$	1,949

Cash and cash equivalents in the table above exclude cash of $2.1 billion as of December 31, 2014 and $622 million as of December 31, 2013.

The following table summarizes our portfolio of available-for-sale securities by contractual maturity (in millions):

	December 31, 2014
	Amortized Cost		Fair Value
Less than one year	$	8,027	$	8,027
Greater than one year but less than five years	1,583		1,580
Greater than five years but less than ten years	14		14
Greater than ten years	4		4
Total	$	9,628	$	9,625

The following table summarizes the gross realized gains and losses related to sales of marketable securities (in millions):

	Year Ended December 31,
	2014		2013			2012
Gross realized gains on sales	$	1	$	1		$	10
Gross realized losses on sales	$	—	$	(1	)	$	(44	)

The following table summarizes our available-for-sale debt securities that were in a continuous unrealized loss position, but were not deemed to be other-than-temporarily impaired (in millions):

	Less Than 12 Months					12 Months or Greater				Total
	Gross Unrealized Losses			Estimated Fair Value		Gross Unrealized Losses		Estimated Fair Value		Gross Unrealized Losses			Estimated Fair Value
December 31, 2014
Debt securities:
Corporate debt securities	$	(3	)	$	802	$	—	$	—	$	(3	)	$	802
Residential mortgage and asset-backed securities	—			227		—		1		—			228
U.S. treasury securities	—			206		—		—		—			206
U.S. government agencies securities	—			22		—		—		—			22
Municipal debt securities	—			2		—		—		—			2
Total	$	(3	)	$	1,259	$	—	$	1	$	(3	)	$	1,260
December 31, 2013
Debt securities:
Corporate debt securities	$	—		$	37	$	—	$	2	$	—		$	39
Residential mortgage and asset-backed securities	—			19		—		6		—			25
U.S. treasury securities	—			25		—		—		—			25
U.S. government agencies securities	—			11		—		—		—			11
Municipal debt securities	—			—		—		—		—			—
Total	$	—		$	92	$	—	$	8	$	—		$	100

We held a total of 468 positions as of December 31, 2014 and 40 positions as of December 31, 2013 that were in an unrealized loss position. The unrealized losses were immaterial both individually and in aggregate. Based on our review of these securities, we believe we had no other-than-temporary impairments on these securities as of December 31, 2014 and 2013 because we do not intend to sell these securities and we believe it is not more likely than not that we will be required to sell these securities before the recovery of their amortized cost basis.