Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Net loss	$ (17,980)	$ (9,674)	$ (10,897)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation and amortization	7,289	7,662	7,643
Inventory provision	67	362	380
Change in lease-related performance obligations	(1,173)	(998)	(864)
Share-based Compensation	23,865	20,964	18,196
Amortization of Debt Issuance Costs and Discounts	6,638	3,899	0
Other Operating Activities, Cash Flow Statement	1,016	22	26
Changes in assets and liabilities
Accounts receivable	(2,420)	(5,017)	(10,963)
Other receivables	(2,064)	(2,810)	(120)
Inventories	(293)	(1,898)	1,361
Prepaid expenses and other assets	(880)	(592)	(866)
Deferred commissions	(174)	(2)	121
Accounts payable	1,475	1,527	(611)
Increase (Decrease) in Other Accrued Liabilities	(2,431)	(2,629)
Increase (Decrease) in Other Operating Liabilities			(1,104)
Deferred revenue	2,843	3,482	5,434
Net cash provided by operating activities	15,778	14,298	7,736
Cash flows from investing activities
Payment for purchase of property and equipment	(4,576)	(4,892)	(2,834)
Purchase of short-term investments	(137,508)	(206,824)	(67,426)
Maturities of short-term investments	121,548	72,183	53,831
Net cash used in investing activities	(20,536)	(139,533)	(16,429)
Cash flows from financing activities
Proceeds from issuance of convertible senior notes, net of issuance costs	0	138,854	0
Cash from lease-related performance obligations	1,735	340	693
Proceeds from Issuance of Shares under Incentive and Share-based Compensation Plans, Excluding Stock Options	3,472	3,269	2,750
Proceeds from exercise of stock options	2,440	7,327	7,917
RSUs released and tax settlement	(11,461)	(10,098)	(8,974)
Net cash provided by (used in) financing activities	(3,814)	130,785	2,386
Net increase (decrease) in cash and cash equivalents	(8,572)	5,550	(6,307)
Cash and cash equivalents at beginning of period	34,276	28,726	35,033
Cash and cash equivalents at end of period	25,704	34,276	28,726
Supplemental cash flow information
Interest Paid, Including Capitalized Interest, Operating and Investing Activities	2,156	1,066	0
Cash paid for income taxes	345	216	342
Supplemental disclosure of non-cash investing and financing activities
Property and equipment in accounts payable and accrued liabilities	458	114	102
Payment for purchase of capped calls	$ 0	$ (8,907)	$ 0