Balance Sheets Details

12 Months Ended

Dec. 31, 2019

Balance Sheet Related Disclosures [Abstract]

Accounts receivable

The following is a summary of activity in our allowance for doubtful accounts for the periods presented (in thousands):


	December 31,
	2019		2018		2017
Allowance - beginning of period	$	(34)	$	(34)	$	(421)


Write-offs and other⁽¹⁾	—		—		387
Allowance - end of period	$	(34)	$	(34)	$	(34)

⁽¹⁾ The change in allowance for doubtful accounts was mainly related to the write-off of receivables from a foreign customer.

Inventories

Inventories consisted of the following (in thousands):


	December 31,
	2019		2018
Raw materials	$	7	$	165
Work in process	26		47
Finished goods	338		377
Inventories	$	371	$	589

Property and Equipment, net

Property and equipment, net consisted of the following (in thousands):


	December 31,
	2019		2018
Laboratory equipment ⁽¹⁾	$	23,561	$	21,328
Leasehold improvements	10,804		10,359
Computer equipment and software	3,016		3,954
Office equipment and furniture	1,461		1,272
Construction in progress ⁽²⁾	691		939
Property and equipment	39,533		37,852
Less: accumulated depreciation and amortization	(33,251)		(33,093)

Property and equipment, net	$	6,282	$	4,759

⁽¹⁾ Fully depreciated laboratory equipment with a cost of $1.0 million and $0.3 million were retired during the year ended December 31, 2019 and 2018, respectively.

⁽²⁾ Construction in progress includes equipment received but not yet placed into service pending installation.

Goodwill

Goodwill had a carrying value of approximately of $3.2 million as of December 31, 2019 and 2018.

Other Accrued Liabilities

Other accrued liabilities consisted of the following (in thousands):


	December 31,
	2019		2018
Accrued purchases	4,386		$	1,492
Accrued professional and outside service fees	1,802		2,020
Deferred rent	—		343
Lease incentive obligation	—		425
Other	352		575
Total	$	6,540	$	4,855