Financial Instruments

12 Months Ended

Dec. 31, 2023

Investments, Debt and Equity Securities [Abstract]

Investments in Marketable Debt Securities

As of December 31, 2023, the weighted-average remaining contractual life, amortized cost, gross unrealized gains, gross unrealized losses, and fair value of marketable debt securities, which were considered as available-for-sale, by type of security were as follows (in thousands):


	December 31, 2023
	Weighted- Average Remaining Contractual Life (in years)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value

Current:

Foreign bonds	0.8	$	54	$	—	$	—	$	54
Mutual funds		40		—		(1)		39
Current portion		94		—		(1)		93
Noncurrent:
Foreign bonds	3.3	939		—		(48)		891

Total		$	1,033	$	—	$	(49)	$	984

As of December 31, 2022, the weighted-average remaining contractual life, amortized cost, gross unrealized gains, gross unrealized losses, and fair value of marketable debt securities, which were considered as available-for-sale, by type of security were as follows (in thousands):


	December 31, 2022
	Weighted- Average Remaining Contractual Life (in years)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value

Current:


Mutual funds		$	38	$	—	$	(2)	$	36

Noncurrent:
Foreign bonds	4.5	932		—		(92)		840

Total		$	970	$	—	$	(94)	$	876

As of December 31, 2023, 12 of the securities were in an unrealized loss position. Accumulated unrealized losses on marketable debt securities that have been in a continuous loss position for less than 12 months and more than 12 months were as follows (in thousands):


	December 31, 2023
	Less than 12 months				More than 12 months
	Estimated Fair Value		Gross Unrealized Losses		Estimated Fair Value		Gross Unrealized Losses


Mutual funds	$	39	$	(1)	$	—	$	—
Foreign bonds	891		(48)		—		—
Total	$	930	$	(49)	$	—	$	—


	December 31, 2022
	Less than 12 months				More than 12 months
	Estimated Fair Value		Gross Unrealized Losses		Estimated Fair Value		Gross Unrealized Losses


Mutual funds	$	—	$	—	$	36	$	(2)
Foreign bonds	—		—		840		(92)
Total	$	—	$	—	$	876	$	(94)

During the years ended December 31, 2023, 2022 and 2021, we evaluated our securities for other-than-temporary impairment and did not recognize any other-than-temporary impairment losses.

Marketable Equity Securities

As of December 31, 2023 and 2022, we held investments in marketable equity securities with readily determinable fair values of $0.9 million and $2.5 million, respectively. During the years ended December 31, 2023, 2022 and 2021, unrealized losses recorded on these securities totaled $1.6 million, $4.2 million, and $4.6 million, respectively, in interest and investment income (loss), net, on the consolidated statements of operations.