Investments

6 Months Ended

Jun. 30, 2017

Available-for-sale Securities [Abstract]

Investments

Investments

Marketable Securities

The following is a summary of our available-for-sale investment securities, excluding those securities classified within cash and cash equivalents on the condensed consolidated balance sheets (in thousands):

	June 30, 2017
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Available-for-sale securities:
Commercial paper	$	68,075	$	—	$	—		$	68,075
Corporate notes and bonds	656,402		123		(878		)	655,647
Certificates of deposit	36,389		—		—			36,389
U.S. government agency securities	56,323		—		(134		)	56,189
Marketable equity securities	10,000		12,214		—			22,214
Total available-for-sale securities	$	827,189	$	12,337	$	(1,012	)	$	838,514

	December 31, 2016
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Available-for-sale securities:
Commercial paper	$	56,839	$	—	$	—		$	56,839
Corporate notes and bonds	628,054		91		(1,590		)	626,555
Certificates of deposit	35,355		—		—			35,355
U.S. government agency securities	42,088		7		(62		)	42,033
Total available-for-sale securities	$	762,336	$	98	$	(1,652	)	$	760,782

As of June 30, 2017, the contractual maturities of our available-for-sale investment securities, excluding marketable equity securities, did not exceed 24 months. The fair values of these securities, by remaining contractual maturity, are as follows (in thousands):

	June 30, 2017
Due in 1 year or less	$	496,505
Due in 1 to 2 years	319,795
Total	$	816,300

The following table shows the fair values and the gross unrealized losses of our available-for-sale investment securities, classified by the length of time that the securities have been in a continuous unrealized loss position, and aggregated by investment types (in thousands): 

	June 30, 2017
	Less than 12 Months					12 Months or Greater					Total
	Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses
Corporate notes and bonds	$	511,868	$	(877	)	$	3,775	$	(1	)	$	515,643	$	(878	)
U.S. government agency securities	65,175		(134		)	—		—			65,175		(134		)
Total	$	577,043	$	(1,011	)	$	3,775	$	(1	)	$	580,818	$	(1,012	)

	December 31, 2016
	Less than 12 Months					12 Months or Greater					Total
	Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses
Corporate notes and bonds	$	492,503	$	(1,530	)	$	47,940	$	(60	)	$	540,443	$	(1,590	)
U.S. government agency securities	30,033		(62		)	—		—			30,033		(62		)
Total	$	522,536	$	(1,592	)	$	47,940	$	(60	)	$	570,476	$	(1,652	)

There were no impairments considered "other-than-temporary" as it is more likely than not we will hold the securities until maturity or a recovery of the cost basis.

Strategic Investments

Our strategic investments consist of debt and non-marketable equity investments in privately-held companies. Debt investments in privately-held companies are classified as available-for-sale and are recorded at their estimated fair value with changes in fair value recorded through accumulated other comprehensive income, while non-marketable equity securities are recorded at cost. We have not recorded any impairment charges for any of our investments in privately-held companies. The total amount of debt and equity investments in privately-held companies included in Other assets on the condensed consolidated balance sheets was $4.9 million and $11.0 million as of June 30, 2017 and December 31, 2016, respectively. During the six months ended June 30, 2017, we reclassified $10.0 million of non-marketable equity securities (at cost) to Short-term investments on our condensed consolidated balance sheets due to an initial public offering by the investee, and recorded an unrealized gain of $12.2 million within other comprehensive income in our consolidated statements of comprehensive loss. During the six months ended June 30, 2017, we also acquired an additional $3.9 million in strategic investments. The fair value of our debt investments in privately-held companies included within our strategic investments is $1.4 million and $0.5 million as of June 30, 2017 and December 31, 2016, respectively. These investments are recorded at fair value using significant unobservable inputs or data in an inactive market and the valuation requires our judgment due to the absence of quoted prices in active markets and inherent lack of liquidity and are categorized accordingly as Level 3 in the fair value hierarchy.