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INVESTMENTS (Tables)

3 Months Ended

Mar. 31, 2021

INVESTMENTS

Summary of investments in available-for-sale


														Continuous			Continuous
					Gross			Gross						Unrealized			Unrealized
					Unrealized			Unrealized						Loss Position			Loss Position
		Amortized			Holding			Holding			Fair			less than 12			greater than 12
March 31, 2021		Cost			Gains			Losses			Value			Months			Months
Available-for-sale
Short-term:
Commercial paper		$	166,306		$	—		$	—		$	166,306		$	—		$	—
Certificates of deposit			40,517			3			—			40,520			—			—
U.S. government agency securities			87,645			16			3			87,658			3			—
U.S. treasuries			685,521			123			20			685,624			20			—
Long-term:
U.S. government agency securities			8,141			—			5			8,136			5			—
U.S. treasuries			55,620			1			6			55,615			6			—
Total		$	1,043,750		$	143		$	34		$	1,043,859		$	34		$	—


														Continuous			Continuous
					Gross			Gross						Unrealized			Unrealized
					Unrealized			Unrealized						Loss Position			Loss Position
		Amortized			Holding			Holding			Fair			less than 12			greater than 12
December 31, 2020		Cost			Gains			Losses			Value			Months			Months
Available-for-sale
Short-term:
Commercial paper		$	119,886		$	—		$	—		$	119,886		$	—		$	—
Certificates of deposit			20,387			—			—			20,387			—			—
Municipal securities			9,083			—			—			9,083			—			—
U.S. government agency securities			81,521			13			3			81,531			3			—
U.S. treasuries			650,386			150			69			650,467			69			—
Long-term:
U.S. government agency securities			10,350			1			—			10,351			—			—
U.S. treasuries			33,946			1			7			33,940			7			—
Total		$	925,559		$	165		$	79		$	925,645		$	79		$	—

Summary of the underlying contractual maturities of investments


		March 31, 2021						December 31, 2020
		Amortized Cost			Fair Value			Amortized Cost			Fair Value
Less than 1 year:
Commercial paper		$	166,306		$	166,306		$	119,886		$	119,886
Municipal securities			—			—			9,083			9,083
U.S. government agency securities			87,645			87,658			81,521			81,531
Certificates of deposit			40,517			40,520			20,387			20,387
U.S. treasuries			685,521			685,624			650,386			650,467
Due 1 - 10 years:
U.S. treasuries			55,620			55,615			33,946			33,940
U.S. government agency securities			8,141			8,136			10,350			10,351
Total		$	1,043,750		$	1,043,859		$	925,559		$	925,645