Available-for-sale securities

12 Months Ended

Dec. 31, 2017

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 summarizes our available-for-sale securities (in millions):

	December 31, 2017									December 31, 2016
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value		Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Corporate debt securities	$	14,790	$	3	$	(46	)	$	14,747	$	12,657	$	7	$	(61	)	$	12,603
Certificates of deposit	5,131		—		—			5,131		943		—		—			943
Money market funds	4,714		—		—			4,714		5,464		—		—			5,464
U.S. treasury securities	4,090		—		(29		)	4,061		5,558		1		(30		)	5,529
Residential mortgage and asset-backed securities	4,072		1		(15		)	4,058		3,613		2		(13		)	3,602
U.S. government agencies securities	934		—		(8		)	926		981		—		(6		)	975
Non-U.S. government securities	668		—		(4		)	664		725		—		(5		)	720
Municipal debt securities	—		—		—			—		27		—		—			27
Equity securities	357		278		—			635		357		71		—			428
Total	$	34,756	$	282	$	(102	)	$	34,936	$	30,325	$	81	$	(115	)	$	30,291

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

	December 31, 2017		December 31, 2016
Cash and cash equivalents	$	5,195	$	5,712
Short-term marketable securities	17,922		3,666
Prepaid and other current assets	635		—
Long-term marketable securities	11,184		20,485
Other long-term assets	—		428
Total	$	34,936	$	30,291

Cash and cash equivalents in the table above excludes cash of $2.4 billion and $2.5 billion as of December 31, 2017 and 2016, respectively.

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

	December 31, 2017
	Amortized Cost		Fair Value
Within one year	$	23,139	$	23,117
After one year through five years	11,125		11,051
After five years through ten years	98		96
After ten years	37		37
Total	$	34,399	$	34,301

The following table summarizes our available-for-sale 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, 2017
Corporate debt securities	$	(14	)	$	7,674	$	(32	)	$	3,561	$	(46	)	$	11,235
U.S. treasury securities	(2		)	821		(27		)	3,240		(29		)	4,061
Residential mortgage and asset-backed securities	(4		)	2,245		(11		)	1,206		(15		)	3,451
U.S. government agencies securities	(1		)	206		(7		)	700		(8		)	906
Non-U.S. government securities	(1		)	203		(3		)	461		(4		)	664
Total	$	(22	)	$	11,149	$	(80	)	$	9,168	$	(102	)	$	20,317
December 31, 2016
Corporate debt securities	$	(60	)	$	8,685	$	(1	)	$	155	$	(61	)	$	8,840
U.S. treasury securities	(30		)	5,081		—			—		(30		)	5,081
Residential mortgage and asset-backed securities	(13		)	2,180		—			42		(13		)	2,222
U.S. government agencies securities	(6		)	897		—			—		(6		)	897
Non-U.S. government securities	(5		)	714		—			5		(5		)	719
Certificates of deposit	—			15		—			—		—			15
Municipal debt securities	—			11		—			—		—			11
Total	$	(114	)	$	17,583	$	(1	)	$	202	$	(115	)	$	17,785

We held a total of 2,957 and 2,709 positions as of December 31, 2017 and 2016, respectively, related to our debt securities that were in an unrealized loss position.

Based on our review of our available-for-sale securities, we believe we had no other-than-temporary impairments on these securities as of December 31, 2017 and 2016, because we do not intend to sell these securities nor do we believe that we will be required to sell these securities before the recovery of their amortized cost basis. Gross realized gains and gross realized losses were immaterial for the years ended December 31, 2017, 2016 and 2015.