INVESTMENTS

Short-term and Long-term Investments in Available for Sale Securities

The following table summarizes, by major security type, the Company's investments as of December 31, 2015 (in thousands):



	Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Short-term investments:
Foreign government securities	$	395,404	$	497	$	(104	)	$	395,797
U.S. government securities	457,001		—		(507		)	456,494
Corporate debt securities	305,654		25		(419		)	305,260
Commercial paper	11,688		—		—			11,688
U.S. government agency securities	2,009		—		(2		)	2,007
Total short-term investments	$	1,171,756	$	522	$	(1,032	)	$	1,171,246

Long-term investments:
Foreign government securities	$	718,947	$	1,367	$	(683	)	$	719,631
U.S. government securities	580,155		277		(1,982		)	578,450
Corporate debt securities	4,294,282		1,273		(18,941		)	4,276,614
U.S. municipal securities	1,080		3		—			1,083
Ctrip convertible debt securities	1,250,000		158,600		(30,050		)	1,378,550
Ctrip equity securities	630,311		346,724		—			977,035
Total long-term investments	$	7,474,775	$	508,244	$	(51,656	)	$	7,931,363

The Company's investment policy seeks to preserve capital and maintain sufficient liquidity to meet operational and other needs of the business. As of December 31, 2015, the weighted-average life of the Company’s fixed income investment portfolio, excluding the Company's investment in Ctrip convertible debt securities, was approximately 2.0 years with an average credit quality of A/A2/A.

The Company invests in foreign government securities with high credit quality. As of December 31, 2015, investments in foreign government securities principally included debt securities issued by the governments of Germany, the Netherlands, France, Belgium and Austria.

On May 26, 2015 and August 7, 2014, the Company invested $250 million and $500 million, respectively, in five-year senior convertible notes issued at par by Ctrip.com International Ltd. ("Ctrip"). On December 11, 2015, the Company invested $500 million in a ten-year senior convertible note issued at par value, which included a put option allowing the Company to require a prepayment in cash from Ctrip at the end of the sixth year of the note. As of December 31, 2015, the Company had also invested $630.3 million of its international cash in Ctrip American Depositary Shares ("ADSs"). The convertible debt and equity securities of Ctrip have been marked-to-market in accordance with the accounting guidance for available-for-sale securities.

In connection with the purchase of the convertible note in August 2014, Ctrip granted the Company the right to appoint an observer to Ctrip's board of directors and permission to acquire Ctrip shares (through the acquisition of Ctrip ADSs in the open market) over the twelve months following the purchase date, so that combined with ADSs issuable upon conversion of this note, the Company could hold up to 10% of Ctrip's outstanding equity. In connection with the purchase of the convertible note in May 2015, Ctrip granted the Company permission to acquire additional Ctrip shares (through the acquisition of Ctrip ADSs in the open market) over the twelve months following the purchase date, so that combined with ADSs issuable upon conversion of the August 2014 and May 2015 notes, the Company could hold up to an aggregate of 15% of Ctrip's outstanding equity. Under the terms of the December 2015 convertible note, the ADSs into which this debt could be converted will not be included in the aggregate 15% ownership holding. As of December 31, 2015, the Company did not have a significant influence over Ctrip. In addition, the Company may acquire the additional ADSs without a time limitation.

The following table summarizes, by major security type, the Company's investments as of December 31, 2014 (in thousands):



	Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Short-term investments:
Foreign government securities	$	52,524	$	—	$	(34	)	$	52,490
U.S. government securities	364,276		24		(34		)	364,266
Corporate debt securities	582,160		15		(652		)	581,523
Commercial paper	39,092		—		—			39,092
U.S. government agency securities	104,829		—		(18		)	104,811
Total short-term investments	$	1,142,881	$	39	$	(738	)	$	1,142,182

Long-term investments:
Foreign government securities	$	12,707	$	—	$	(36	)	$	12,671
U.S. government securities	557,130		80		(762		)	556,448
U.S. corporate debt securities	2,332,030		2,299		(5,296		)	2,329,033
U.S. government agency securities	95,108		97		(111		)	95,094
U.S. municipal securities	1,114		—		(12		)	1,102
Ctrip corporate debt securities	500,000		—		(74,039		)	425,961
Ctrip equity securities	421,930		—		(86,586		)	335,344
Total long-term investments	$	3,920,019	$	2,476	$	(166,842	)	$	3,755,653

The Company has classified its investments as available-for-sale securities. These securities are carried at estimated fair value with the aggregate unrealized gains and losses related to these investments, net of taxes, reflected as a part of "Accumulated other comprehensive income (loss)" in the Consolidated Balance Sheets. Classification as short-term or long-term is based upon the maturity of the debt securities.

The Company recognized $2.2 million of net realized gains related to investments for the year ended December 31, 2015. There were no significant realized gains or losses related to investments for the year ended December 31, 2014.

Cost Method Investments

The Company held investments in equity securities of private companies of approximately $62.3 million and $0.6 million as of December 31, 2015 and December 31, 2014, respectively. These investments are accounted for under the cost method and included in "Other assets" in the Company's Consolidated Balance Sheets. As of December 31, 2015, the Company did not estimate the fair value of these cost-method investments because there were no identified events or changes in circumstances that may have a significant adverse impact on the carrying values of these investments.