Note 3. Balance Sheet Details

Short-term investments

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


	At September 30, 2017
	Maturity	Amortized cost		Unrealized		Unrealized		Estimated
	(in years)	or cost		gains		losses		fair value
U.S. government bonds	less than 2	$	1,800	$	-	$	(12)	$	1,788
U.S. government agency bonds	less than 3		3,698		-		(11)		3,687
Bank certificates of deposit	less than 1		7,498		5		-		7,503
Commercial paper	less than 1		9,174		2		-		9,176
Corporate notes	less than 3		53,419		29		(29)		53,419
Asset-backed securities	less than 3		13,933		1		(13)		13,921
		$	89,522	$	37	$	(65)	$	89,494

	At December 31, 2016
	Maturity	Amortized cost		Unrealized		Unrealized		Estimated
	(in years)	or cost		gains		losses		fair value
U.S. government agency bonds	1-3	$	9,535	$	2	$	(22)	$	9,515
Bank certificates of deposit	less than 2		11,101		13		(1)		11,113
Commercial paper	less than 1		17,011		1		(2)		17,010
Corporate notes	less than 3		45,178		7		(61)		45,124
Asset-backed securities	less than 2		6,503		3		—		6,506
		$	89,328	$	26	$	(86)	$	89,268

Accounts receivable, net

Accounts receivable consisted of the following (in thousands):


	September 30,		December 31,
	2017		2016
Accounts receivable	$	17,568	$	14,800
Less allowance for doubtful accounts		(620)		(495)
	$	16,948	$	14,305

Inventory, net

Inventory consisted of the following (in thousands):

Accrued liabilities

Accrued liabilities consisted of the following (in thousands):


	September 30,		December 31,
	2017		2016
Accrued contract payments (see Note 8)	$	1,000	$	823
Accrued sales commissions		2,065		1,641
Accrued clinical study payments		643		1,167
Accrued bonuses		4,565		6,122
Accrued vacation benefits		2,033		1,382
Accrued Employee Stock Purchase Plan deductions		865		4
Other accrued liabilities		4,986		2,772
	$	16,157	$	13,911