	As of
	June 28, 2020										December 31, 2019
	Cost		Unrealized Gains		Unrealized Losses		Allowance for Credit Losses		Estimated Fair Value		Cost		Unrealized Gains		Unrealized Losses		Estimated Fair Value
	(In thousands)
Certificates of deposit	$	147	$	—	$	—	$	—	$	147	$	149	$	—	$	—	$	149
Convertible debt		1,326		—		—		—		1,326		1,326		—		—		1,326
Total	$	1,473	$	—	$	—	$	—	$	1,473	$	1,475	$	—	$	—	$	1,475

The Company’s available-for-sale short-term investments are primarily comprised of convertible debt securities with an original maturity or remaining maturity at the time of purchase of greater than three months and no more than twelve months. Accordingly, none of the available-for-sale investments have unrealized losses greater than twelve months.

	As of
	June 28, 2020		December 31, 2019
	(In thousands)
Raw materials	$	14,751	$	28,871
Finished goods		135,834		206,618
Total	$	150,585	$	235,489

The Company records provisions for excess and obsolete inventory based on assumptions about future demand and market conditions and the amounts incurred were $2.2 million and $4.6 million for the three and six months ended June 28, 2020, respectively, and $1.1 million and $2.0 million for the three and six months ended June 30, 2019, respectively. While management believes the estimates and assumptions underlying its current forecasts are reasonable, there is risk that additional charges may be necessary if current forecasts are greater than actual demand.

	As of
	June 28, 2020			December 31, 2019
	(In thousands)
Computer equipment	$	10,376		$	9,883
Furniture, fixtures and leasehold improvements		18,134			18,623
Software		28,718			27,865
Machinery and equipment		67,268			59,637
Total property and equipment, gross		124,496			116,008
Accumulated depreciation and amortization		(108,960	)		(98,325	)
Total	$	15,536		$	17,683

Depreciation and amortization expense pertaining to property and equipment was $3.2 million and $6.2 million for the three and six months ended June 28, 2020, respectively, and $3.2 million and $6.1 million for the three and six months ended June 30, 2019, respectively.

	As of June 28, 2020							As of December 31, 2019
	Gross		Accumulated Amortization			Net		Gross		Accumulated Amortization			Net
	(In thousands)
Technology	$	59,799	$	(57,621	)	$	2,178	$	59,799	$	(57,406	)	$	2,393
Customer contracts and relationships		56,800		(52,978	)		3,822		56,800		(50,297	)		6,503
Other		10,345		(9,430	)		915		10,345		(9,137	)		1,208
Total	$	126,944	$	(120,029	)	$	6,915	$	126,944	$	(116,840	)	$	10,104

Amortization of intangibles was $1.6 million and $3.2 million for the three and six months ended June 28, 2020, respectively, and $1.7 million and $3.8 million for the three and six months ended June 30, 2019, respectively.

As of June 28, 2020, estimated amortization expense related to finite-lived intangibles for the remaining years is as follows (in thousands):

2020 (remaining six months)	$	3,016
2021		2,044
2022		527
2023		514
2024		514
Thereafter		300
Total estimated amortization expense	$	6,915

	As of
	June 28, 2020		December 31, 2019
	(In thousands)
Non-current deferred income taxes	$	56,065	$	58,930
Long-term investments		9,869		8,147
Other		6,403		7,202
Total	$	72,337	$	74,279

The Company’s long-term investments are primarily comprised of equity investments without readily determinable fair values. The changes in the carrying value of these investments during the following periods are as follows:

	Six Months Ended
	June 28, 2020			June 30, 2019
	(In thousands)
Carrying value as of the beginning of the period	$	8,147		$	2,886
Additions from purchase of investments		5,815			5,200
Impairment		(4,530	)		—
Carrying value as of the end of the period ⁽¹⁾	$	9,432		$	8,086

⁽¹⁾The balance as of June 28, 2020 did not include the investment in limited partnership fund of $0.4 million.

The impairment recognized during the first fiscal quarter of 2020 was brought about by triggering events impacting the valuation of a number of its privately held long-term investments, partially due to the onset of the COVID-19 pandemic. No impairment pertaining to long-lived assets was recognized during the three months ended June 28, 2020. For the equity investments without readily determinable fair values as of June 28, 2020, cumulative downward adjustments for price changes and impairment was $6.2 million and cumulative upward adjustments for price changes was $0.2 million.

	As of
	June 28, 2020		December 31, 2019
	(In thousands)
Current operating lease liabilities	$	8,896	$	9,357
Sales and marketing		58,104		85,605
Warranty obligations		9,275		10,556
Sales returns⁽¹⁾		49,107		52,612
Freight and duty		8,610		5,633
Other		29,087		25,784
Total	$	163,079	$	189,547

⁽¹⁾Inventory expected to be received from future sales returns amounted to $24.9 million and $26.8 million as of June 28, 2020 and December 31, 2019, respectively. Provisions to write down expected returned inventory to net realizable value amounted to $14.4 million and $14.9 million as of June 28, 2020 and December 31, 2019, respectively.