MARKETABLE DEBT SECURITIES (Tables)

3 Months Ended

Mar. 31, 2020

Investments, Debt and Equity Securities [Abstract]

Summary of Company's Marketable Debt Securities

The following tables summarize our marketable debt securities:

	As of March 31, 2020
(In thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Certificates of deposit	$	5,141	$	—	$	(7)	$	5,134
Commercial paper	21,792		—		—		21,792
Corporate notes	114,592		9		(321)		114,280
U.S. government-sponsored enterprise securities	105,028		275		(6)		105,297
U.S. treasury securities	722,103		4,232		—		726,335
Total	$	968,656	$	4,516	$	(334)	$	972,838

	As of December 31, 2019
(In thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Certificates of deposit	$	4,303	$	—	$	(2)	$	4,301
Commercial paper	39,913		—		—		39,913
Corporate notes	146,016		58		(34)		146,040
U.S. government-sponsored enterprise securities	32,487		3		(2)		32,488
U.S. treasury securities	1,092,293		185		(71)		1,092,407
Total	$	1,315,012	$	246	$	(109)	$	1,315,149

Summary of Fair Value of Marketable Debt Securities

The fair values of our marketable debt securities by classification in the condensed consolidated balance sheets were as follows:

(In thousands)	As of March 31, 2020		As of December 31, 2019
Cash and cash equivalents	$	136,492	$	340,132
Marketable debt securities	836,346		975,017
Total	$	972,838	$	1,315,149