CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Operating Activities
Net loss	$ (21,157)	$ (14,730)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization	2,674	5,063
Amortization of lease right-of-use assets	2,405
Loss on disposal of fixed assets	26	83
Stock-based compensation	23,923	19,036
Unrealized foreign currency losses	469	1,541
Amortization of discount on short-term investments	(298)	(205)
Deferred rent and other liabilities	3,666	1,491
Changes in operating assets and liabilities:
Accounts receivable, net	(5,828)	(3,209)
Inventory, net	414	(2,511)
Prepaid expenses and other current assets	(2,326)	(1,695)
Accounts payable and accrued liabilities	(60)	(2,000)
Other assets	(86)	(1,128)
Net cash provided by operating activities	3,822	1,736
Investing activities
Purchases of short-term investments	(64,726)	(70,100)
Proceeds from sales and maturities of short-term investments	61,870	64,185
Purchases of property and equipment	(3,530)	(2,733)
Net cash used in investing activities	(6,386)	(8,648)
Financing activities
Proceeds from exercise of stock options	14,005	16,418
Proceeds from share purchases under Employee Stock Purchase Plan	3,388	3,509
Payments of employee taxs related to vested restricted stock units	(5,002)	(325)
Net cash provided by financing activities	12,391	19,602
Effect of exchange rate changes on cash and cash equivalents	(8)	80
Net increase in cash, cash equivalents and restricted cash	9,819	12,770
Cash, cash equivalents and restricted cash at beginning of period	38,596	24,508
Cash, cash equivalents and restricted cash at end of period	48,415	37,278
Supplemental disclosures of cash flow information
Taxes paid	$ 96	$ 13