Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Cash flows from operating activities:
Net loss	$ (1,022)	$ (2,051)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	1,395	1,332
Depreciation and amortization	248	240
Other	(51)	12
Changes in assets and liabilities:
Accounts receivable	(1,305)	472
Inventories	(695)	(1,397)
Other current assets and prepaid expenses	(158)	(230)
Other long-term assets	(9)	(35)
Accounts payable	491	611
Accrued liabilities	(2,657)	(2,758)
Other long-term liabilities		(82)
Deferred revenue	(23)	(103)
Income tax liability	1	(55)
Net cash used in operating activities	(3,785)	(4,044)
Cash flows from investing activities:
Acquisition of property, equipment and software	(69)	(97)
Disposal of property and equipment	25
Proceeds from sales of marketable investments	5,255	1,800
Proceeds from maturities of marketable investments	14,035	3,975
Purchase of marketable investments	(15,972)	(6,399)
Net cash provided by (used in) investing activities	3,274	(721)
Cash flows from financing activities:
Repurchase of common stock	(2,700)	(279)
Proceeds from exercise of stock options and employee stock purchase plan	1,751	744
Taxes paid related to net share settlement of equity awards	(784)	(233)
Payments on capital lease obligations	(88)	(70)
Net cash (used in) provided by financing activities	(1,821)	162
Net decrease in cash and cash equivalents	(2,332)	(4,603)
Cash and cash equivalents at beginning of period	13,775	10,868
Cash and cash equivalents at end of period	11,443	6,265
Supplemental disclosure of non-cash items:
Repurchase of common stock acquired but not settled	207	27
Assets acquired under capital lease	$ 80	$ 51