Investments

At December 31, 2015 and 2014, the estimated fair value of our short-term and long-term investments classified as available for sale, are as follows:



	December 31, 2015
	Gross Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(In millions)
Short-term investments:
Restricted cash	$	28	$	—	$	—		$	28
Corporate debt securities	3,302		1		(16		)	3,287
Government and agency securities	55		—		—			55
Equity instruments	9		920		—			929
	$	3,394	$	921	$	(16	)	$	4,299
Long-term investments:
Corporate debt securities	3,327		7		(67		)	3,267
	$	3,327	$	7	$	(67	)	$	3,267



	December 31, 2014
	Gross Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(In millions)
Short-term investments:
Restricted cash	$	19	$	—	$	—		$	19
Corporate debt securities	2,519		1		(1		)	2,519
Government and agency securities	3		—		—			3
Time deposits and other	152		—		—			152
Equity instruments	9		1,028		—			1,037
	$	2,702	$	1,029	$	(1	)	$	3,730
Long-term investments:
Corporate debt securities	5,319		18		(18		)	5,319
Government and agency securities	232		1		—			233
	$	5,551	$	19	$	(18	)	$	5,552

At December 31, 2015 and 2014, we held no time deposits classified as held to maturity.

At December 31, 2015, investment securities in a continuous loss position for greater than 12 months had an estimated fair value and unrealized loss of $769 million and $40 million respectively. We had no material long-term or short-term investments that have been in a continuous unrealized loss position for more than 12 months as of December 31, 2014. As of December 31, 2015, these securities had a weighted average remaining duration of approximately 12 months. Refer to "Note 19 - Accumulated Other Comprehensive Income" for amounts reclassified to earnings from unrealized gains and losses.

Our fixed-income investment portfolio consists of predominantly investment grade corporate debt securities and government and agency securities that have a maximum maturity of 8 years. The corporate debt and government and agency securities that we invest in are generally deemed to be low risk based on their credit ratings from the major rating agencies. The longer the duration of these securities, the more susceptible they are to changes in market interest rates and bond yields. As interest rates increase, those securities purchased at a lower yield show a mark-to-market unrealized loss. The unrealized losses are due primarily to changes in credit spreads and interest rates. We regularly review investment securities for other-than-temporary impairment using both qualitative and quantitative criteria. We presently do not intend to sell any of the securities in an unrealized loss position and expect to realize the full value of all these investments upon maturity or sale. Restricted cash is held primarily in interest bearing accounts for letters of credit related primarily to our global sabbatical program and various lease arrangements.

The estimated fair values of our short-term and long-term investments classified as available for sale by date of contractual maturity at December 31, 2015 are as follows:



	December 31, 2015
	(In millions)
One year or less (including restricted cash of $28)	$	3,370
One year through two years	1,190
Two years through three years	1,464
Three years through four years	547
Four years through five years	59
Five years through six years	—
Six years through seven years	—
Seven years through eight years	6
Eight years through nine years	—
Nine years through ten years	—
	$	6,636

Equity and cost method investments

We have made multiple equity and cost method investments which are reported in long-term investments on our consolidated balance sheet. As of December 31, 2015 and 2014, our equity and cost method investments totaled $124 million and $184 million, respectively. During the second quarter of 2015, we sold our equity interest in craigslist, Inc. During the third quarter of 2015, we sold a portion of our equity interest in Jasper Infotech Private Limited (Snapdeal) and our entire interest in Baixing Holdings Limited. The resulting gains are recorded in interest and other, net on our consolidated statement of income.