Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
CASH FLOWS FROM OPERATING ACTIVITIES
Net loss	$ (48,365)	$ (25,777)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock based compensation expense	18,907	15,789
Change in fair value of derivatives		(1,850)
Depreciation and amortization	1,446	672
Loss on extinguishment of warrant liability		520
Amortization of intangible assets	99	33
Amortization of debt discount	28	11
Change in fair value of contingent consideration	(48)	20
Other non-cash adjustments	30
Changes in operating assets and liabilities:
Accounts receivable	(624)	(332)
Inventory	(26)	(249)
Prepaid expenses and other current assets	(486)	2
Operating lease right-of-use assets	791
Other assets	25	(137)
Accounts payable and accrued expenses	(17)	448
Other current liabilities	367
Deferred revenue	(126)
Operating lease liabilities	(670)
Other long-term liabilities	(120)	89
Net cash used in operating activities	(28,789)	(10,761)
CASH FLOWS FROM INVESTING ACTIVITIES
Purchase of property and equipment	(2,110)	(4,163)
Purchase of available-for-sale securities	(15,445)
Proceeds from maturities of available-for-sale securities	9,278
Acquisition of IBEX		(2,258)
Net cash used in investing activities	(8,277)	(6,421)
CASH FLOWS FROM FINANCING ACTIVITIES
Net proceeds from the sale of common stock	27,948	92,676
Proceeds from stock options exercised	529	64
Proceeds from ESPP purchase	35
Cash paid for tax withholdings related to net share settlement	(636)
Payment of contingent consideration liability	(109)
Principal payments on financing leases	(225)
Principal payments on term note payable	(262)
Net cash provided by financing activities	27,280	92,740
Net (decrease) increase in cash and cash equivalents	(9,786)	75,558
Cash and cash equivalents - beginning of period	55,673	12,517
Cash and cash equivalents - end of period	45,887	88,075
Supplemental schedule of non-cash investing and financing activities:
Conversion of Series A, B, E preferred stock to common stock		109,104
Exchange of Series F preferred stock for common stock		13,061
Extinguishment of warrant liability		2,525
Unpaid liability for acquisition of property and equipment	63	441
Deemed dividend - accretion of discount on Series F preferred stock		698
Cumulative dividends on Series F preferred stock		191
Series F preferred stock dividends paid in common stock		306
Unpaid tax liability related to net share settlement	43
Unrealized gain on short-term investments and cash equivalents	43
Reclassification of stock-based compensation expense that was previously classified as a liability to paid-in capital	38
Contingent consideration for IBEX acquisition		278
Contingent consideration earned and recorded in accounts payable		30
Note payable issued as partial consideration for IBEX acquisition		$ 1,220