Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Operating activities:
Net loss	$ (4,694)	$ (7,460)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	238	326
Loss (Gain) on disposal of property and equipment	1	(1)
Stock-based compensation	1,980	1,669
Unrealized gain on investment in marketable securities	(26)	0
Changes in operating assets and liabilities:
Accounts receivable, net	3,890	543
Inventories	(177)	(299)
Prepaid expenses and other current assets	(427)	(168)
Accounts payable	(975)	(882)
Accrued compensation	1,381	1,020
Other accrued liabilities	705	763
Long term lease incentive	(106)	(106)
Other long term liabilities	(104)	(19)
Deferred revenue	(5,871)	1,048
Net cash used in operating activities	(4,185)	(3,566)
Investing activities:
Purchase of property and equipment	(16)	(237)
Proceeds from disposal of property and equipment	0	1
Net cash used in investing activities	(16)	(236)
Financing activities:
Proceeds from exercises of stock options	434	99
Principal payments on capital lease obligations	(58)	(10)
Taxes paid related to net share settlement of equity awards	(3,140)	(1,636)
Net cash used in financing activities	(2,764)	(1,547)
Net decrease in cash, cash equivalents and restricted cash	(6,965)	(5,349)
Cash, cash equivalents and restricted cash at the beginning of the period	25,811	15,515
Cash, cash equivalents and restricted cash at the end of the period	32,776	20,864
Supplemental disclosure of cash flow information:
Interest paid	22	3
Income taxes paid	5	1
Supplemental non-cash investing and financing activities:
Equipment acquired under capital leases	0	528
Purchase of property and equipment recorded in accounts payable and accrued expenses	15	68
Cash and cash equivalents	24,300	13,923
Total cash, cash equivalents and restricted cash at the end of the period	$ 32,776	$ 20,864