Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (21,990)	$ (8,353)	$ (26,804)	$ (36,314)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization			1,586	1,004
Stock-based compensation			2,873	1,782
Accretion on asset retirement obligation			20	19
Change in fair value of warrant liabilities			(7,009)	9,032
Loss on disposal of property and equipment			0	9
Amortization of debt discount and interest accrual			1,770	1,605
Changes in operating assets and liabilities:
Accounts receivable			6,763	2,380
Inventory			(10,312)	(7,276)
Deposits on purchased inventory			(499)	(2,994)
Deferred cost of revenue			(2,447)	(7,254)
Prepaid expenses and other assets			(1,079)	(2,096)
Accounts payable			(3,383)	1,808
Accrued expenses and other long-term liabilities			679	976
Customer deposits and deferred revenue			(10,996)	13,436
Net cash used in operating activities			(48,838)	(23,883)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchase of property and equipment			(2,280)	(776)
Net cash used in investing activities			(2,280)	(776)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from common stock private placement, gross			0	26,100
Proceeds from the exercise of stock options			715	193
Net cash provided by financing activities			59,910	64,388
NET INCREASE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH			8,792	39,729
CASH, CASH EQUIVALENTS AND RESTRICTED CASH — BEGINNING OF PERIOD			58,532	15,341	$ 15,341
CASH, CASH EQUIVALENTS AND RESTRICTED CASH — END OF PERIOD	$ 67,324	$ 55,070	67,324	55,070	58,532
SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION:
Cash paid for interest			2,014	1,924
Cash paid for taxes			0	1
SUPPLEMENTAL NON-CASH INVESTING AND FINANCING ACTIVITIES:
Transfer of property and equipment from inventory and deferred cost of revenue			1,577	0
Purchase of property and equipment in accounts payable and accrued expenses			13	248
Offering cost in accounts payable and accrued expenses			0	6
Private Placement
CASH FLOWS FROM FINANCING ACTIVITIES:
Payment of offering costs related to common stock issuance			0	(300)
At The Market Offering Program
CASH FLOWS FROM FINANCING ACTIVITIES:
Payment of offering costs related to common stock issuance			(6)	(1,129)
Proceeds from offering of common stock, gross			278	39,524	$ 40,100
Direct Registered Offering
CASH FLOWS FROM FINANCING ACTIVITIES:
Payment of offering costs related to common stock issuance			(177)
Proceeds from offering of common stock, gross			$ 59,100	$ 0