Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Operating activities:
Net loss	$ (5,136)	$ (4,694)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	319	238
Amortization expense - right-of-use assets - operating and finance leases	759
Loss on disposal of property and equipment	0	1
Stock-based compensation	2,063	1,980
Unrealized gain on investment in equity securities	103	(26)
Changes in operating assets and liabilities:
Accounts receivable, net	(1,053)	3,603
Inventories	(44)	(177)
Prepaid expenses and other current assets	(163)	(427)
Contract assets	35	0
Unbilled receivables	(7)	287
Other non-current assets	38	0
Accounts payable	(999)	(975)
Accrued compensation	1,196	1,381
Other accrued liabilities	3,591	705
Other long term liabilities	(616)	(210)
Deferred revenue	(2,937)	(5,871)
Net cash used in operating activities	(2,851)	(4,185)
Investing activities:
Purchase of property and equipment	(445)	(16)
Net cash used in investing activities	(445)	(16)
Financing activities:
Proceeds from exercises of stock options	776	434
Payments of lease obligations - Finance leases	(59)	(58)
Taxes paid related to net share settlement of equity awards	(2,799)	(3,140)
Net cash used in financing activities	(2,082)	(2,764)
Net decrease in cash, cash equivalents and restricted cash	(5,378)	(6,965)
Cash, cash equivalents and restricted cash at the beginning of the period	54,485	32,776
Cash, cash equivalents and restricted cash at the end of the period	49,107	25,811
Supplemental disclosure of cash flow information
Interest paid	22	22
Income taxes paid	0	5
Purchase of property and equipment recorded in accounts payable and accrued expenses	142	15
Cash and cash equivalents	47,322	24,300
Total cash, cash equivalents and restricted cash at the end of the period	$ 54,485	$ 32,776