INVESTMENTS

12 Months Ended

Dec. 31, 2023

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, 2023	Cost		Gains		Losses		Value		Months		12 Months
Available-for-sale
Short-term:
Commercial paper	$	163,775	$	—	$	1	$	163,774	$	1	$	—
Certificates of deposit		15,590		—		—		15,590		—		—
Municipal securities		361		—		—		361		—		—
U.S. government agency securities		116,524		90		66		116,548		66		—
U.S. treasuries		412,936		205		1,084		412,057		1,084		—
Corporate bonds		247,340		89		154		247,275		154		—
Long-term:
U.S. government agency securities		23,485		51		5		23,531		5		—
U.S. treasuries		35,896		79		8		35,967		8		—
Corporate bonds		16,903		32		2		16,933		2		—
Total	$	1,032,810	$	546	$	1,320	$	1,032,036	$	1,320	$	—

									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	$	—

During the years ended December 31, 2023, 2022 and 2021, realized gains or losses recognized on the sale of investments were not significant.

The Company’s investments at December 31, 2023 and 2022 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, 2023				December 31, 2022
	Amortized Cost		Fair Value		Amortized Cost		Fair Value
Less than 1 year:
Commercial paper	$	163,775	$	163,774	$	197,712	$	197,710
Municipal securities		361		361		211,791		211,239
U.S. government agency securities		116,524		116,548		109,697		108,985
Certificates of deposit		15,590		15,590		10,078		10,078
U.S. treasuries		412,936		412,057		838,825		834,302
Corporate bonds		247,340		247,275		—		—
Due 1 - 10 years:
U.S. treasuries		35,896		35,967		53,215		53,164
U.S. government agency securities		23,485		23,531		2,016		2,013
Variable rate demand notes		—		—		4,862		4,862
Corporate bonds		16,903		16,933		—		—
Due 11 - 20 years:
Variable rate demand notes		—		—		1,404		1,404
Total	$	1,032,810	$	1,032,036	$	1,429,600	$	1,423,757