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	$ (64,159)	$ (26,804)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	2,033	1,586
Stock-based compensation	9,459	2,873
Accretion on asset retirement obligation	14	20
Change in fair value of warrant liabilities	6,935	(7,009)
Amortization of debt discount and interest accrual	184	1,770
Product upgrade reserve	5,523	0
Changes in operating assets and liabilities:
Accounts receivable	1,392	6,763
Inventory	(8,810)	(10,312)
Deposits on purchased inventory	2,350	(499)
Deferred cost of revenue	(577)	(2,447)
Prepaid expenses and other assets	796	(1,079)
Accounts payable	8,256	(3,383)
Accrued expenses and other long-term liabilities	3,791	679
Customer deposits and deferred revenue	(16,739)	(10,996)
Net cash used in operating activities	(49,552)	(48,838)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property and equipment	(4,353)	(2,280)
Net cash used in investing activities	(4,353)	(2,280)
CASH FLOWS FROM FINANCING ACTIVITIES:
Payment of debt issuance cost	(168)	0
Proceeds from the exercise of stock options	8,203	715
Net cash provided by financing activities	8,035	59,910
NET (DECREASE) INCREASE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH	(45,870)	8,792
CASH, CASH EQUIVALENTS AND RESTRICTED CASH — BEGINNING OF PERIOD	169,365	58,532
CASH, CASH EQUIVALENTS AND RESTRICTED CASH — END OF PERIOD	123,495	67,324
SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION:
Cash paid for interest	1,811	2,014
Cash paid for taxes	7	0
SUPPLEMENTAL NON-CASH INVESTING AND FINANCING ACTIVITIES:
Fair value of common stock warrants reclassified from liability to additional paid-in capital upon exercise	2,105	0
Right-of-use assets obtained in exchange for new operating lease liabilities	1,647	0
Transfer of property and equipment from inventory and deferred cost of revenue	4,394	1,577
Purchase of property and equipment in accounts payable and accrued liabilities	1,146	13
At The Market Offering Program
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from offering of common stock, gross	0	278
Payment of offering costs related to common stock issuance	0	(6)
Direct Registered Offering
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from offering of common stock, gross	0	59,100
Payment of offering costs related to common stock issuance	$ 0	$ (177)