Investments

At December 31, 2014 and 2013, the estimated fair value of our short-term and long-term investments classified as available for sale, are as follows:



	December 31, 2014
	Gross Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(In millions)
Short-term investments:
Restricted cash	$	29	$	—	$	—		$	29
Corporate debt securities	2,519		1		(1		)	2,519
Government and agency securities	3		—		—			3
Time deposits and other	181		—		—			181
Equity instruments	10		1,028		—			1,038
	$	2,742	$	1,029	$	(1	)	$	3,770
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



	December 31, 2013
	Gross Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(In millions)
Short-term investments:
Restricted cash	$	17	$	—	$	—		$	17
Corporate debt securities	3,525		4		—			3,529
Government and agency securities	43		—		—			43
Time deposits and other	49		—		—			49
Equity instruments	12		881		—			893
	$	3,646	$	885	$	—		$	4,531
Long-term investments:
Corporate debt securities	4,409		41		(5		)	4,445
Government and agency securities	250		1		—			251
	$	4,659	$	42	$	(5	)	$	4,696

At December 31, 2014, we held no time deposits classified as held to maturity, compared to $6 million as of December 31, 2013, which were recorded at amortized cost.

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 and 2013. 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 corporate debt securities and government and agency securities that have a maximum maturity of nine 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 expect to realize the full value of all these investments upon maturity or sale. As of December 31, 2014, these securities had a weighted average remaining duration of approximately 15 months. Restricted cash is held primarily in money market funds and 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, 2014 are as follows:



	December 31, 2014
	(In millions)
One year or less (including restricted cash of $29)	$	2,732
One year through two years	1,550
Two years through three years	2,055
Three years through four years	1,106
Four years through five years	736
Five years through six years	86
Six years through seven years	2
Seven years through eight years	—
Eight years through nine years	17
Nine years through ten years	—
	$	8,284

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, 2014 and 2013, our equity and cost method investments totaled $225 million and $269 million, respectively.