AVAILABLE-FOR-SALE SECURITIES (Tables)

6 Months Ended

Jun. 30, 2017

Investments Schedule [Abstract]

Amortized Cost, Gross Unrealized Holding Gain or Loss, and Fair Value of Available For Sale Security by Major Security type

The amortized cost, gross unrealized holding gains or losses, and fair value of the Company’s available-for-sale securities by major security type at June 30, 2017 and December 31, 2016 are summarized in the tables below:

	Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses			Aggregate Fair Value at June 30, 2017
Corporate debt securities	$	615,435	$	426	$	(1,411	)	$	614,450
Commercial paper		8,976		—		—			8,976
U.S. government agency securities		233,898		4		(840	)		233,062
Greek government-issued bonds		48		122		(1	)		169
Total	$	858,357	$	552	$	(2,252	)	$	856,657

	Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses			Aggregate Fair Value at December 31, 2016
Certificates of deposit	$	2,800	$	—	$	—		$	2,800
Corporate debt securities		641,670		329		(2,282	)		639,717
Commercial paper		16,075		—		—			16,075
U.S. government agency securities		310,635		37		(747	)		309,925
Greek government-issued bonds		48		86		—			134
Total	$	971,228	$	452	$	(3,029	)	$	968,651

Fair Values of Available-For-Sale Securities by Contractual Maturity

The fair values of available-for-sale securities by contractual maturity were as follows:

	June 30,		December 31,
	2017		2016
Maturing in one year or less	$	374,621	$	395,940
Maturing after one year through five years		482,036		572,711
Total	$	856,657	$	968,651