INVESTMENTS (Tables)

12 Months Ended

Dec. 31, 2015

Investments Schedule [Abstract]

Investments

Investments at December 31, 2015 and 2014 consisted of the following (in thousands):

	Years Ended December 31,
	2015		2014
Certificates of deposit	$	10,078	$	17,438
Commercial paper		23,955		7,498
Corporate debt securities		323,219		174,323
Securities of government-sponsored entities		30,232		1,028
Total investments	$	387,484	$	200,287

Summary of Investments Classified as Available-For-Sale Securities

The following is a summary of investments classified as available-for-sale securities (in thousands):

	Contractual Maturity (in years)	Amortized Cost		Gross Unrealized Gains(1)		Gross Unrealized Losses(1)			Aggregate Estimated Fair Value
December 31, 2015:
Classified as current assets:
Certificates of deposit	Less than 1	$	9,120	$	1	$	(1	)	$	9,120
Commercial paper	Less than 1		23,965		1		(11	)		23,955
Corporate debt securities	Less than 1		254,592		1		(414	)		254,179
Securities of government-sponsored entities	Less than 1		17,762		1		(21	)		17,742
Total short-term available-for-sale securities		$	305,439	$	4	$	(447	)	$	304,996
Classified as non-current assets:
Certificates of deposit	1 to 2	$	960	$	—	$	(2	)	$	958
Corporate debt securities	1 to 2		69,528		—		(488	)		69,040
Securities of government-sponsored entities	1 to 2		12,534		—		(44	)		12,490
Total long-term available-for-sale securities		$	83,022	$	—	$	(534	)	$	82,488
December 31, 2014:
Classified as current assets:
Certificates of deposit	Less than 1	$	9,072	$	—	$	(6	)	$	9,066
Commercial paper	Less than 1		7,497		1		—			7,498
Corporate debt securities	Less than 1		145,321		5		(123	)		145,203
Securities of government-sponsored entities	Less than 1		1,029		—		(1	)		1,028
Total short-term available-for-sale securities		$	162,919	$	6	$	(130	)	$	162,795
Classified as non-current assets:
Certificates of deposit	1 to 2	$	8,400	$	—	$	(28	)	$	8,372
Corporate debt securities	1 to 2		29,245		—		(125	)		29,120
Total long-term available-for-sale securities		$	37,645	$	—	$	(153	)	$	37,492

(1) Unrealized gains and losses are included in other comprehensive loss.

Gross Unrealized Losses and Fair Value Available-For-Sale Investments in Unrealized Loss Position

The following table presents gross unrealized losses and fair value for those available-for-sale investments that were in an unrealized loss position as of December 31, 2015 and 2014, aggregated by investment category and length of time that individual securities have been in a continuous loss position (in thousands):

	Less Than 12 Months					12 Months or Greater					Total
	Estimated Fair Value		Unrealized Losses			Estimated Fair Value		Unrealized Losses			Estimated Fair Value		Unrealized Losses
December 31, 2015:
Certificates of deposit	$	5,517	$	(3	)	$	—	$	—		$	5,517	$	(3	)
Commercial paper		16,959		(11	)		—		—			16,959		(11	)
Corporate debt securities		310,160		(880	)		5,521		(22	)		315,681		(902	)
Securities of government-sponsored entities		25,913		(65	)		—		—			25,913		(65	)
Total	$	358,549	$	(959	)	$	5,521	$	(22	)	$	364,070	$	(981	)
December 31, 2014:
Certificates of deposit	$	16,957	$	(34	)	$	—	$	—		$	16,957	$	(34	)
Corporate debt securities		149,477		(248	)		—		—			149,477		(248	)
Securities of government-sponsored entities		1,028		(1	)		—		—			1,028		(1	)
Total	$	167,462	$	(283	)	$	—	$	—		$	167,462	$	(283	)