Investments (Tables)

6 Months Ended

Jun. 30, 2017

Investments [Abstract]

Fair value of short and long-term investments classified as available for sale

The following tables summarize the unrealized gains and losses and estimated fair value of our investments classified as available-for-sale as of June 30, 2017 and December 31, 2016 (in millions):

	June 30, 2017
	Gross Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Short-term investments:
Restricted cash	$	21	$	—	$	—		$	21
Corporate debt securities (1)	6,302		2		(12		)	6,292
Government and agency securities	68		—		—			68
	$	6,391	$	2	$	(12	)	$	6,381
Long-term investments:
Corporate debt securities (1)	4,611		19		(6		)	4,624
	$	4,611	$	19	$	(6	)	$	4,624

(1) As of June 30, 2017, investment securities with a fair value of $393 million and a net unrealized foreign exchange loss of $11 million were held by a foreign subsidiary in which the U.S. dollar is not the functional currency.

	December 31, 2016
	Gross Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Short-term investments:
Restricted cash	$	19	$	—	$	—		$	19
Corporate debt securities	5,203		44		(1		)	5,246
Government and agency securities	63		5		—			68
	$	5,285	$	49	$	(1	)	$	5,333
Long-term investments:
Corporate debt securities	3,848		15		(12		)	3,851
	$	3,848	$	15	$	(12	)	$	3,851

Estimated fair values of short and long-term investments classified by date of contractual maturity

The estimated fair values of our short-term and long-term investments classified as available-for-sale by date of contractual maturity as of June 30, 2017 are as follows (in millions):  

	June 30, 2017
One year or less (including restricted cash of $21)	$	6,381
One year through two years	2,154
Two years through three years	1,683
Three years through four years	208
Four years through five years	504
Five years through six years	75
	$	11,005