Note 3. Balance Sheet Details

Short-term investments

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


	At June 30, 2017
	Maturity	Amortized cost		Unrealized		Unrealized		Estimated
	(in years)	or cost		gains		losses		fair value
U.S. government bonds	1-3	$	1,799	$	-	$	(12)	$	1,787
U.S. government agency bonds	less than 3		3,697		-		(12)		3,685
Bank certificates of deposit	less than 1		15,450		8		-		15,458
Commercial paper	less than 1		8,327		1		-		8,328
Corporate notes	less than 3		53,435		20		(39)		53,416
Asset-backed securities	less than 2		7,747		1		(2)		7,746
		$	90,455	$	30	$	(65)	$	90,420

	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):


	June 30,		December 31,
	2017		2016
Accounts receivable	$	17,196	$	14,800
Less allowance for doubtful accounts		(494)		(495)
	$	16,702	$	14,305

Inventory, net

Inventory consisted of the following (in thousands):

Accrued liabilities

Accrued liabilities consisted of the following (in thousands):


	June 30,		December 31,
	2017		2016
Accrued contract payments (see Note 5)	$	1,025	$	823
Accrued sales commissions		382		1,641
Accrued clinical study payments		783		1,167
Accrued bonuses		4,863		6,122
Accrued vacation benefits		1,731		1,382
Accrued Employee Stock Purchase Plan deductions		491		4
Other accrued liabilities		3,786		2,772
	$	13,061	$	13,911