INVESTMENTS

12 Months Ended

Dec. 31, 2022

INVESTMENTS

INVESTMENTS

5.          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
December 31, 2022	Cost		Gains		Losses		Value		Months		12 Months
Available-for-sale
Short-term:
Commercial paper	$	197,712	$	1	$	4	$	197,709	$	4	$	—
Certificates of deposit		10,078		—		—		10,078		—		—
Municipal securities		211,791		60		612		211,239		612		—
U.S. government agency securities		109,697		3		715		108,985		715		—
U.S. treasuries		838,825		17		4,539		834,303		4,539		—
Long-term:
U.S. government agency securities		2,016		—		3		2,013		3		—
U.S. treasuries		53,215		20		71		53,164		71		—
Variable rate demand notes		6,266		—		—		6,266		—		—
Total	$	1,429,600	$	101	$	5,944	$	1,423,757	$	5,944	$	—

									Continuous		Continuous
			Gross		Gross				Unrealized		Unrealized
			Unrealized		Unrealized				Loss Position		Loss Position
	Amortized		Holding		Holding		Fair		less than 12		greater than
December 31, 2021	Cost		Gains		Losses		Value		Months		12 Months
Available-for-sale
Short-term:
Commercial paper	$	334,077	$	—	$	—	$	334,077	$	—	$	—
Certificates of deposit		44,502		—		—		44,502		—		—
Municipal securities		666		—		—		666		—		—
U.S. government agency securities		62,687		—		26		62,661		26		—
U.S. treasuries		1,308,536		2		717		1,307,821		717		—
Long-term:
U.S. government agency securities		12,500		—		24		12,476		24		—
U.S. treasuries		87,133		—		190		86,943		190		—
Total	$	1,850,101	$	2	$	957	$	1,849,146	$	957	$	—

During the years ended December 31, 2022, 2021 and 2020, realized gains or losses recognized on the sale of investments were not significant.

The Company’s investments at December 31, 2022 and 2021 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, 2022				December 31, 2021
	Amortized Cost		Fair Value		Amortized Cost		Fair Value
Less than 1 year:
Commercial paper	$	197,712	$	197,710	$	334,077	$	334,077
Municipal securities		211,791		211,239		666		666
U.S. government agency securities		109,697		108,985		62,687		62,661
Certificates of deposit		10,078		10,078		44,502		44,502
U.S. treasuries		838,825		834,302		1,308,536		1,307,821
Due 1 - 10 years:
U.S. treasuries		53,215		53,164		87,133		86,943
U.S. government agency securities		2,016		2,013		12,500		12,476
Variable rate demand notes		4,862		4,862		—		—
Due 11 - 20 years:
Variable rate demand notes		1,404		1,404		—		—
Total	$	1,429,600	$	1,423,757	$	1,850,101	$	1,849,146