INVESTMENTS (Tables)

3 Months Ended

Mar. 31, 2018

Investments consist of the following (in thousands):

	March 31, 2018		December 31, 2017
Commercial paper	$	41,993	$	75,362
Corporate debt securities		501,103		414,815
Securities of government sponsored entities		18,391		18,401
Total investments	$	561,487	$	508,578

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
March 31, 2018:
Classified as current assets:
Commercial paper	Less than 1	$	42,105	$	—	$	(112	)	$	41,993
Corporate debt securities	Less than 1		236,818		—		(1,127	)		235,691
Securities of government-sponsored entities	Less than 1		7,501		—		(17	)		7,484
Total short-term available-for-sale securities		$	286,424	$	—	$	(1,256	)	$	285,168
Classified as non-current assets:
Corporate debt securities	1 to 2	$	267,756	$	—	$	(2,344	)	$	265,412
Securities of government-sponsored entities	1 to 2		11,004		—		(97	)		10,907
Total long-term available-for-sale securities		$	278,760	$	—	$	(2,441	)	$	276,319
December 31, 2017:
Classified as current assets:
Commercial paper	Less than 1	$	75,396	$	1	$	(35	)	$	75,362
Corporate debt securities	Less than 1		178,776		—		(400	)		178,376
Securities of government-sponsored entities	Less than 1		7,503		—		(24	)		7,479
Total short-term available-for-sale securities		$	261,675	$	1	$	(459	)	$	261,217
Classified as non-current assets:
Corporate debt securities	1 to 2	$	237,749	$	—	$	(1,310	)	$	236,439
Securities of government-sponsored entities	1 to 2		11,004		—		(82	)		10,922
Total long-term available-for-sale securities		$	248,753	$	—	$	(1,392	)	$	247,361

(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 March 31, 2018 and December 31, 2017, 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
March 31, 2018:
Commercial paper	$	41,993	$	(112	)	$	—	$	—		$	41,993	$	(112	)
Corporate debt securities		481,836		(3,409	)		19,267		(62	)		501,103		(3,471	)
Securities of government-sponsored entities		10,907		(97	)		7,484		(17	)		18,391		(114	)
Total	$	534,736	$	(3,618	)	$	26,751	$	(79	)	$	561,487	$	(3,697	)
December 31, 2017:
Commercial paper	$	62,602	$	(35	)	$	—	$	—		$	62,602	$	(35	)
Corporate debt securities		386,728		(1,660	)		28,087		(50	)		414,815		(1,710	)
Securities of government-sponsored entities		10,922		(82	)		7,479		(24	)		18,401		(106	)
Total	$	460,252	$	(1,777	)	$	35,566	$	(74	)	$	495,818	$	(1,851	)

- Definition

Tabular disclosure of available-for-sale securities which includes, but is not limited to, changes in the cost basis and fair value, fair value and gross unrealized gain (loss), fair values by type of security, contractual maturity and classification, amortized cost basis, contracts to acquire securities to be accounted for as available-for-sale, debt maturities, transfers to trading, change in net unrealized holding gain (loss) net of tax, continuous unrealized loss position fair value, aggregate losses qualitative disclosures, other than temporary impairment (OTTI) losses or other disclosures related to available for sale securities.

+ References + Details