The following tables summarize the unrealized gains and losses and estimated fair value of our investments classified as available-for-sale as of September 30, 2018 and December 31, 2017 (in millions):



	September 30, 2018
	Gross Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Short-term investments:
Restricted cash	$	15	$	—	$	—		$	15
Corporate debt securities	2,702		1		(7		)	2,696
Government and agency securities	41		—		—			41
	$	2,758	$	1	$	(7	)	$	2,752
Long-term investments:
Corporate debt securities	4,171		7		(46		)	4,132
	$	4,171	$	7	$	(46	)	$	4,132



	December 31, 2017
	Gross Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Short-term investments:
Restricted cash	$	20	$	—	$	—		$	20
Corporate debt securities	3,726		1		(4		)	3,723
	$	3,746	$	1	$	(4	)	$	3,743
Long-term investments:
Corporate debt securities	5,458		12		(24		)	5,446
	$	5,458	$	12	$	(24	)	$	5,446

Investment securities in a continuous loss position for greater than 12 months had an estimated fair value of $696 million and $14 million of unrealized losses as of September 30, 2018 and an estimated fair value of $360 million and an immaterial amount of unrealized losses as of December 31, 2017. Refer to “Note 14 - Accumulated Other Comprehensive Income” for amounts reclassified to earnings from unrealized gains and losses.

The estimated fair values of our short-term and long-term investments classified as available-for-sale by date of contractual maturity as of September 30, 2018 are as follows (in millions):



	September 30, 2018
One year or less (including restricted cash of $15)	$	2,752
One year through two years	1,973
Two years through three years	1,451
Three years through four years	591
Four years through five years	117
	$	6,884

Our equity investments are reported in long-term investments on our condensed consolidated balance sheet. The following table provides a summary of our equity investments as of September 30, 2018 and December 31, 2017 (in millions):



	September 30, 2018		December 31, 2017
Equity investments without readily determinable fair values	$	138	$	872
Equity investments under the equity method of accounting	6		13
Total equity investments	$	144	$	885

During the third quarter of 2018, we sold our investment in Flipkart. The $313 million gain upon sale of the investment was recorded in interest and other, net on our condensed consolidated statement of income. During the second quarter of 2018, we relinquished our existing equity method investment in Giosis as part of the exchange for the acquisition of Giosis’ Japan business. The $266 million gain upon relinquishment was recorded in interest and other, net on our condensed consolidated statement of income. Refer to “Note 3 - Business Combinations” for further details on the acquisition.

The following table provides a summary of unrealized gains and losses recorded in interest and other, net during the three and nine months ended September 30, 2018 related to equity investments without readily determinable fair values still held at September 30, 2018.



	Three Months Ended September 30, 2018			Nine Months Ended September 30, 2018
Net gains/(losses) recognized during the period on equity investments	$	313		$	313
Less: Net gains/(losses) recognized during the period on equity investments sold during the period	(313		)	(313		)
Total unrealized gains/(losses) on equity investments still held at September 30, 2018	$	—		$	—

The following table summarizes the total carrying value of equity investments without readily determinable fair values during the three and nine months ended September 30, 2018 (in millions):



	Three Months Ended September 30, 2018			Nine Months Ended September 30, 2018
Carrying value, beginning of period	$	859		$	872
Additions	—			23
Sales	(718		)	(718		)
Downward adjustments for observable price changes and impairment	—			(20		)
Foreign currency translation and other	(3		)	(19		)
Carrying value, end of period	$	138		$	138