Note 3. Balance Sheet Details

Short-term investments

Short-term investments consisted of the following (in thousands):


		At December 31, 2018
	Maturity	Amortized cost		Unrealized		Unrealized		Estimated
	(in years)	or cost		gains		losses		fair value
U.S. government bonds	less than 1	$	1,300	$	—	$	(3)	$	1,297
U.S. government agency bonds	less than 1		1,994		—		(12)		1,982
Bank certificates of deposit	less than 2		15,201		2		(3)		15,200
Commercial paper	less than 1		9,597		1		(5)		9,593
Corporate notes	less than 3		60,923		24		(194)		60,753
Asset-backed securities	less than 3		21,918		18		(94)		21,842
Total		$	110,933	$	45	$	(311)	$	110,667


		At December 31, 2017
	Maturity	Amortized cost		Unrealized		Unrealized		Estimated
	(in years)	or cost		gains		losses		fair value
U.S government bonds	less than 2	$	1,799	$	—	$	(17)	$	1,782
U.S. government agency bonds	less than 2		2,698		—		(17)		2,681
Bank certificates of deposit	less than 1		10,300		1		(3)		10,298
Commercial paper	less than 1		11,598		—		(5)		11,593
Corporate notes	less than 3		51,532		6		(121)		51,417
Asset-backed securities	less than 3		16,796		—		(61)		16,735
Total		$	94,723	$	7	$	(224)	$	94,506

Accounts receivable, net

Accounts receivable consisted of the following (in thousands):


	December 31,
	2018		2017

Accounts receivable	$	19,333	$	17,248
Allowance for doubtful accounts		(660)		(592)
	$	18,673	$	16,656

Inventory, net

Inventory consisted of the following (in thousands):


	December 31,
	2018		2017

Finished goods	$	4,256	$	4,225
Work in process		3,197		2,368
Raw material		5,829		4,629
	$	13,282	$	11,222

Property and equipment, net

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


	December 31,
	2018		2017

Buildings	$	874	$	874
Equipment		10,306		8,311
Furniture and fixtures		1,570		1,382
Leasehold improvements		4,792		4,568
Computer equipment and software		2,232		1,980
Land		7,068		—
Construction in progress		1,231		1,134
		28,073		18,249
Less accumulated depreciation and amortization		(8,920)		(6,455)
	$	19,153	$	11,794

Depreciation and amortization expense related to property and equipment was $3.1 million, $2.1 million and $1.1 million for the years ended December 31, 2018, December 31, 2017 and December 31, 2016, respectively.

Accrued liabilities

Accrued liabilities consisted of the following (in thousands):


	December 31,
	2018		2017

Accrued bonuses	$	8,604	$	9,106
Accrued legal expenses		2,466		591
Accrued vacation benefits		2,446		2,121
Accrued Employee Stock Purchase Plan liability		1,154		1,517
Other accrued liabilities		9,294		7,114
	$	23,964	$	20,449