SHORT-TERM INVESTMENTS (Tables)

6 Months Ended

Jun. 30, 2016

SHORT-TERM INVESTMENTS

Schedule of short-term investments

        As of June 30, 2016, short-term investments consisted of the following:

	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Available-for-sale securities:
Corporate notes and bonds	$	403,094	$	1,480	$	(135	)	$	404,439
U.S. agency obligations		82,969		79		(1	)		83,047
U.S. treasury securities		74,741		185		(1	)		74,925
Commercial paper		16,869		3		(3	)		16,869
Certificates of deposit		4,803		5		—			4,808
Total available-for-sale securities	$	582,476	$	1,752	$	(140	)	$	584,088

        As of December 31, 2015, short-term investments consisted of the following:

	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Available-for-sale securities:
Corporate notes and bonds	$	390,185	$	12	$	(2,321	)	$	387,876
U.S. agency obligations		121,521		11		(203	)		121,329
U.S. treasury securities		60,362		2		(179	)		60,185
Commercial paper		36,849		—		(28	)		36,821
Certificates of deposit		7,928		—		(9	)		7,919
Total available-for-sale securities	$	616,845	$	25	$	(2,740	)	$	614,130

Summary of estimated fair value of short-term investments, designated as available-for-sale and classified by the contractual maturity

	June 30, 2016		December 31, 2015
Due in one year or less	$	223,684	$	206,679
Due after one year through three years		360,404		407,451
Total	$	584,088	$	614,130

Schedule of fair values and gross unrealized losses of available-for-sale securities aggregated by investment category

        The following table shows the fair values and the gross unrealized losses of available-for-sale securities that have been in a gross unrealized loss position, aggregated by investment category as of June 30, 2016:

	Estimated Fair Value		Gross Unrealized Losses
Corporate notes and bonds	$	145,463	$	(135	)
U.S. agency obligations		12,056		(1	)
U.S. treasury securities		708		(1	)
Commercial paper		4,959		(3	)
	$	163,186	$	(140	)