Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities:
Net income (loss)	$ (4,477)	$ 7,113
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Stock-based compensation	5,524	3,623
Depreciation of tangible assets	849	750
Amortization of contract acquisition costs	1,304
Change in deferred tax assets	(3,507)
Provision for doubtful accounts receivable	(877)	9
Other	215	(58)
Changes in assets and liabilities:
Accounts receivable	(5,544)	(3,048)
Inventories	(2,540)	(8,751)
Other current assets and prepaid expenses	(797)	(633)
Other long-term assets	(2,301)	(1)
Accounts payable	6,319	3,207
Accrued liabilities	(4,177)	4,757
Other long-term liabilities	105
Deferred revenue	58	652
Income tax liability	(27)	3
Net cash provided by (used in) in operating activities	(8,119)	7,605
Cash flows from investing activities:
Acquisition of property, equipment and software	(1,214)	(443)
Disposal of property and equipment	41	53
Proceeds from sales of marketable investments	13,044	9,154
Proceeds from maturities of marketable investments	8,050	39,612
Purchase of marketable investments	(4,390)	(44,156)
Net cash provided by investing activities	15,531	4,220
Cash flows from financing activities:
Repurchase of common stock		(13,776)
Proceeds from exercise of stock options and employee stock purchase plan	3,603	4,566
Taxes paid related to net share settlement of equity awards	(2,971)	(1,332)
Payments on capital lease obligations	(362)	(274)
Net cash provided by (used) in financing activities	270	(10,816)
Net increase in cash and cash equivalents	7,682	1,009
Cash and cash equivalents at beginning of period	14,184	13,775
Cash and cash equivalents at end of period	21,866	14,784
Supplemental disclosure of non-cash items:
Assets acquired under capital lease	$ 610	$ 257