CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Operating Activities
Net (loss) income	$ (1,098)	$ 4,388
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Depreciation and amortization	3,941	3,410
Loss on disposal of fixed assets	5
Stock-based compensation	12,653	6,117
Unrealized foreign currency gains	(948)	(311)
Change in fair value of stock warrant liability		(43)
Amortization of premium on short-term investments	55	206
Deferred rent	577	(1)
Change in operating assets and liabilities:
Accounts receivable, net	(2,483)	(4,170)
Inventory	(1,918)	(2,191)
Prepaid expenses and other current assets	568	(1,396)
Restricted cash	80
Accounts payable and accrued liabilities	2,774	2,996
Other assets	(577)	26
Net cash provided by operating activities	13,629	9,031
Investing activities
Purchases of short-term investments	(71,437)	(60,724)
Proceeds from sale and maturities of short-term investments	71,190	41,702
Purchases of property and equipment	(4,453)	(4,236)
Net cash used in investing activities	(4,700)	(23,258)
Financing activities
Proceeds from exercise of stock options	3,266	3,749
Proceeds from exercise of stock warrants		50
Payments of secured notes		(6,656)
Share purchases under Employee Stock Purchase Plan	968	793
Net cash provided by (used in) financing activities	4,234	(2,064)
Effect of exchange rate changes on cash and cash equivalents	(339)	(293)
Net increase (decrease) in cash and cash equivalents	12,824	(16,584)
Cash and cash equivalents at beginning of period	6,494	21,572
Cash and cash equivalents at end of period	19,318	4,988
Supplemental disclosures of cash flow information
Interest paid		253
Taxes paid	64	64
Supplemental schedule of noncash investing and financing activities
Reduction of liability upon vesting of stock options previously exercised for unvested stock	$ 4	$ 54