Available-for-Sale Debt Securities (Tables)

6 Months Ended

Jun. 30, 2018

Debt Securities, Available-for-sale [Abstract]

Summary of Available-for-Sale Securities at Estimated Fair Value

The following table summarizes our available-for-sale debt securities (in millions):



	June 30, 2018									December 31, 2017
	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	$	12,144	$	3	$	(55	)	$	12,092	$	14,790	$	3	$	(46	)	$	14,747
U.S. treasury securities	3,412		—		(21		)	3,391		4,090		—		(29		)	4,061
Residential mortgage and asset-backed securities	2,674		—		(17		)	2,657		4,072		1		(15		)	4,058
U.S. government agencies securities	880		—		(8		)	872		934		—		(8		)	926
Certificates of deposit	3,145		—		—			3,145		5,131		—		—			5,131
Non-U.S. government securities	407		—		(3		)	404		668		—		(4		)	664
Total	$	22,662	$	3	$	(104	)	$	22,561	$	29,685	$	4	$	(102	)	$	29,587

Summary of the Classification of Available-for-Sale Securities

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



	June 30, 2018		December 31, 2017
Cash and cash equivalents	$	4,139	$	481
Short-term marketable securities	12,683		17,922
Long-term marketable securities	5,739		11,184
Total	$	22,561	$	29,587

Summary of Available-for-Sale Securities by Contractual Maturity

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



	June 30, 2018
	Amortized Cost		Fair Value
Within one year	$	16,861	$	16,822
After one year through five years	5,710		5,649
After five years through ten years	67		66
After ten years	24		24
Total	$	22,662	$	22,561

Summary of Available-for-Sale Securities in a Continuous Loss Position Deemed not to be Other-than-Temporarily Impaired

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
June 30, 2018
Corporate debt securities	$	(15	)	$	3,774	$	(40	)	$	3,449	$	(55	)	$	7,223
U.S. treasury securities	(1		)	239		(20		)	2,482		(21		)	2,721
Residential mortgage and asset-backed securities	(5		)	1,176		(12		)	1,167		(17		)	2,343
U.S. government agencies securities	—			46		(8		)	687		(8		)	733
Certificates of deposit	—			71		—			—		—			71
Non-U.S. government securities	—			64		(3		)	323		(3		)	387
Total	$	(21	)	$	5,370	$	(83	)	$	8,108	$	(104	)	$	13,478

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