Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Cash flows from operating activities:
Net loss	$ (12,414,000)	$ (8,220,000)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	1,980,000	1,307,000
Depreciation of tangible assets	360,000	411,000
Amortization of contract acquisition costs	717,000	690,000
Change in deferred tax asset	15,000	6,000
Provision for credit losses	590,000	98,000
Other	35,000	103,000
Changes in assets and liabilities:
Accounts receivable	5,306,000	403,000
Inventories	(3,020,000)	1,355,000
Other current assets and prepaid expenses	807,000	(916,000)
Other long-term assets	(207,000)	(679,000)
Accounts payable	1,919,000	(942,000)
Accrued liabilities	(6,567,000)	(1,467,000)
Extended warranty liabilities	(234,000)	(492,000)
Other long-term liabilities		(140,000)
Deferred revenue	(1,253,000)	525,000
Income tax liabilities		5,000
Net cash used in operating activities	(11,966,000)	(7,953,000)
Cash flows from investing activities:
Acquisition of property, equipment and software	(230,000)	(65,000)
Proceeds from maturities of marketable investments	6,800,000	3,200,000
Purchase of marketable investments	(3,930,000)	(1,586,000)
Net cash provided by investing activities	2,640,000	1,549,000
Cash flows from financing activities:
Proceeds from exercise of stock options and employee stock purchase plan	201,000	131,000
Taxes paid related to net share settlement of equity awards	(2,234,000)	(490,000)
Payments on finance lease obligations	(183,000)	(131,000)
Net cash used in financing activities	(2,216,000)	(490,000)
Net decrease in cash and cash equivalents	(11,542,000)	(6,894,000)
Cash and cash equivalents at beginning of period	26,316,000	26,052,000
Cash and cash equivalents at end of period	14,774,000	19,158,000
Supplemental disclosure of non-cash items:
Assets acquired under capital lease		$ 192,000