Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Cash flows from operating activities:
Net loss	$ (15,916)	$ (12,631)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation, amortization and write-off of property and equipment	1,016	930
Amortization and write-off of intangibles	876	794
Changes in allowance for doubtful accounts		16
Stock-based compensation	4,162	3,857
Changes in operating assets and liabilities:
Trade accounts receivable	2,095	1,842
Other current assets	(437)	(251)
Other assets	(56)	66
Accounts payable and other accrued liabilities	680	280
Deferred revenue	(1,407)	(1,929)
Net cash used in operating activities	(8,987)	(7,026)
Cash flows from investing activities:
Purchase of property and equipment	(1,565)	(747)
Capitalized patent costs	(623)	(646)
Maturity of marketable securities	35,182	27,151
Purchase of marketable securities	(40,817)	(25,786)
Net cash used in investing activities	(7,823)	(28)
Cash flows from financing activities:
Issuance of common stock, net of issuance costs	39,700	12,896
Exercise of stock options	476	1,321
Purchase of common stock	(1,879)	(1,833)
Net cash provided by financing activities	38,297	12,384
Net increase in cash and cash equivalents	21,487	5,330
Cash and cash equivalents at beginning of period	3,160	6,122
Cash and cash equivalents at end of period	24,647	11,452
Supplemental disclosure of cash flow information:
Cash paid for income taxes, net	27	22
Supplemental schedule of non-cash investing activities:
Property and equipment and patent costs in accounts payable	76	73
Stock-based compensation capitalized to software and patent costs	$ 121	$ 137