Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Cash flows from operating activities:
Net income (loss)	$ 7,113	$ (1,636)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Stock-based compensation	3,623	2,652
Depreciation and amortization	750	733
Other	(67)	(45)
Changes in assets and liabilities:
Accounts receivable	(3,048)	(61)
Inventories	(8,751)	(4,400)
Other current assets and prepaid expenses	(633)	(690)
Other long-term assets	(1)	(60)
Accounts payable	3,207	1,324
Accrued liabilities	4,757	886
Other long-term liabilities		(247)
Deferred revenue	652	(1,187)
Income tax liability	3	(18)
Net cash provided by (used) in operating activities	7,605	(2,749)
Cash flows from investing activities:
Acquisition of property, equipment and software	(443)	(311)
Disposal of property and equipment	53	17
Proceeds from sales of marketable investments	9,154	6,153
Proceeds from maturities of marketable investments	39,612	20,135
Purchase of marketable investments	(44,156)	(23,944)
Net cash provided by investing activities	4,220	2,050
Cash flows from financing activities:
Repurchase of common stock	(13,776)	(4,873)
Proceeds from exercise of stock options and employee stock purchase plan	4,566	6,798
Taxes paid related to net share settlement of equity awards	(1,332)	(601)
Payments on capital lease obligations	(274)	(218)
Net cash used in financing activities	(10,816)	1,106
Net increase in cash and cash equivalents	1,009	407
Cash and cash equivalents at beginning of period	13,775	10,868
Cash and cash equivalents at end of period	14,784	11,275
Supplemental disclosure of non-cash items:
Assets acquired under capital lease	$ 257	$ 580