Investments

At March 31, 2016 and December 31, 2015, the estimated fair value of our short-term and long-term investments classified as available for sale, were as follows:



	March 31, 2016
	Gross Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(In millions)
Short-term investments:
Restricted cash	$	25	$	—	$	—		$	25
Corporate debt securities ⁽¹⁾	4,349		2		(56		)	4,295
Government and agency securities	50		—		—			50
Equity instruments	9		948		—			957
	$	4,433	$	950	$	(56	)	$	5,327
Long-term investments:
Corporate debt securities ⁽¹⁾	3,266		16		(42		)	3,240
	$	3,266	$	16	$	(42	)	$	3,240

(1) At March 31, 2016 investment securities with a fair value and an unrealized foreign exchange loss of $1.1 billion and $55 million, respectively, were held by a foreign subsidiary in which the U.S. Dollar is not the functional currency.



	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

At March 31, 2016, investment securities in a continuous loss position for greater than 12 months had an estimated fair value and unrealized loss of $485 million and $35 million, respectively. 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. 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 at March 31, 2016 are as follows:



	March 31, 2016
	(In millions)
One year or less (including restricted cash of $25)	$	4,369
One year through two years	1,476
Two years through three years	1,482
Three years through four years	242
Four years through five years	36
Five years through six years	—
Six years through seven years	—
Seven years through eight years	5
Eight years through nine years	—
Nine years through ten years	—
	$	7,610

Equity and cost method investments

We have made multiple equity and cost method investments which are reported in long-term investments on our condensed consolidated balance sheet. As of March 31, 2016 and December 31, 2015, our equity and cost method investments totaled $130 million and $124 million, respectively.