Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash flows from operating activities:
Net loss	$ (8,112)	$ (6,218)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation, amortization and write-off of property and equipment	380	299
Amortization and write-off of intangibles	146	257
Stock-based compensation	1,671	1,503
Changes in operating assets and liabilities:
Trade accounts receivable	2,614	1,274
Other current assets	304	70
Other assets	44	55
Accounts payable and other accrued liabilities	(420)	128
Deferred revenue	(219)	(498)
Net cash used in operating activities	(3,592)	(3,130)
Cash flows from investing activities:
Purchase of property and equipment	(302)	(605)
Capitalized patent costs	(208)	(200)
Maturity of marketable securities	18,657	16,399
Purchase of marketable securities	(6,961)	(10,561)
Net cash provided by investing activities	11,186	5,033
Cash flows from financing activities:
Exercise of stock options	560	177
Purchase of common stock	(528)	(583)
Net cash provided by (used in) financing activities	32	(406)
Net increase in cash and cash equivalents	7,626	1,497
Cash and cash equivalents at beginning of period	40,823	11,638
Cash and cash equivalents at end of period	48,449	13,135
Supplemental disclosure of cash flow information:
Cash received (paid) for income taxes, net	113	(13)
Supplemental schedule of non-cash investing activities:
Property and equipment and patent costs in accounts payable	(64)	(120)
Stock-based compensation capitalized to software and patent costs	$ 44	$ 45