Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Cash flows from operating activities:
Net loss	$ (3,280)	$ (5,533)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	2,082	1,943
Depreciation and amortization	484	622
Other	(63)	245
Changes in assets and liabilities:
Accounts receivable	464	2,218
Inventories	(2,624)	(2,533)
Other current assets and prepaid expenses	(861)	154
Other long-term assets	(64)	10
Accounts payable	793	514
Accrued liabilities	(773)	(686)
Other long-term liabilities	(164)	(145)
Deferred revenue	(321)	(1,478)
Income tax liability	(25)	35
Net cash used in operating activities	(4,352)	(4,634)
Cash flows from investing activities:
Acquisition of property, equipment and software	(137)	(678)
Disposal of property and equipment	6
Proceeds from sales of marketable investments	5,051	7,379
Proceeds from maturities of marketable investments	10,585	21,350
Purchase of marketable investments	(14,003)	(12,262)
Net cash provided by investing activities	1,502	15,789
Cash flows from financing activities:
Repurchase of common stock	(2,865)	(17,744)
Proceeds from exercise of stock options and employee stock purchase plan	2,394	8,508
Payments on capital lease obligations	(127)	(95)
Net cash used in financing activities	(598)	(9,331)
Net increase (decrease) in cash and cash equivalents	(3,448)	1,824
Cash and cash equivalents at beginning of period	10,868	9,803
Cash and cash equivalents at end of period	7,420	11,627
Supplemental disclosure of non-cash items:
Repurchase of common stock acquired but not settled	84
Assets acquired under capital lease	$ 365