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INVESTMENTS

12 Months Ended

Dec. 31, 2020

INVESTMENTS

INVESTMENTS

4. INVESTMENTS

The following table summarizes the Company’s investments at:


														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		$	—


														Continuous			Continuous
					Gross			Gross						Unrealized			Unrealized
					Unrealized			Unrealized						Loss Position			Loss Position
		Amortized			Holding			Holding			Fair			less than 12			greater than 12
December 31, 2019		Cost			Gains			Losses			Value			Months			Months
Available-for-sale
Short-term:
Commercial paper		$	83,478		$	—		$	—		$	83,478		$	—		$	—
Certificates of deposit			28,049			—			—			28,049			—			—
Municipal securities			147,983			145			20			148,108			20			—
U.S. government agency securities			40,620			5			35			40,590			35			—
U.S. treasuries			211,055			134			31			211,158			31			—
Variable rate demand notes			21,680			—			—			21,680			—			—
Long-term:
Municipal securities			1,562			—			1			1,561			1			—
U.S. government agency securities			5,267			—			1			5,266			1			—
U.S. treasuries			6,077			1			—			6,078			—			—
Total		$	545,771		$	285		$	88		$	545,968		$	88		$	—

During the years ended December 31, 2020, 2019 and 2018, realized gains or losses recognized on the sale of investments were not significant.

The Company’s investments at December 31, 2020 and 2019 carried investment grade credit ratings. Variable rate demand notes (“VRDNs”) are floating rate municipal bonds with embedded put options that allow the bondholder to sell the security at par plus accrued interest. All of the put options are secured by a pledged liquidity source. While they are classified as marketable investment securities, the put option allows the VRDNs to be liquidated at par on a same day, or more generally, on a seven-day settlement basis.

The following table summarizes the underlying contractual maturities of the Company’s investments at:


		December 31, 2020						December 31, 2019
		Amortized Cost			Fair Value			Amortized Cost			Fair Value
Less than 1 year:
Commercial paper		$	119,886		$	119,886		$	83,478		$	83,478
Municipal securities			9,083			9,083			147,983			148,108
U.S. government agency securities			81,521			81,531			40,620			40,590
Certificates of deposit			20,387			20,387			28,049			28,049
U.S. treasuries			650,386			650,467			211,055			211,158
Due 1 -10 years:
Municipal securities			—			—			1,562			1,561
U.S. treasuries			33,946			33,940			6,077			6,078
U.S. government agency securities			10,350			10,351			5,267			5,266
Variable rate demand notes			—			—			3,905			3,905
Due 11 - 20 years:
Variable rate demand notes			—			—			8,886			8,886
Due 21 - 30 years:
Variable rate demand notes			—			—			6,885			6,885
Due 31 - 40 years:
Variable rate demand notes			—			—			2,004			2,004
Total		$	925,559		$	925,645		$	545,771		$	545,968