CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Cash flows from operating activities:
Net income (loss)	$ (11,694)	$ (11,498)	$ (47,928)	$ (50,717)	$ (61,662)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation and amortization	2,311	2,053	6,801	5,524	7,677
Asset write-downs and impairment of field equipment	178	72	320	206	241
Share-based compensation to employees	10,479	8,629	29,205	20,760	27,116
Decrease (increase) in trade receivables	2,255	(9,112)	(3,016)	(16,661)	(23,228)
Amortization of discount (premium)	(555)	17	1,502	226	252
Decrease (increase) in receivables and prepaid expenses	1,322	5,986	(1,789)	4,525	1,979
Decrease (increase) in inventories	(1,735)	504	385	907	3,524
Decrease (increase) in other long-term assets	155	(238)	(743)	(532)	(554)
Increase (decrease) in trade payables	(381)	983	2,848	(4,213)	(1,150)
Increase (decrease) in other payables and accrued expenses	3,220	4,830	(5,608)	8,308	14,460
Increase (decrease) in employee benefit liabilities, net	31	113	108	352	440
Increase (decrease) in other long-term liabilities	52	208	(764)	1,079	(2,229)
Net cash provided by (used in) operating activities	5,638	2,547	(18,679)	(30,236)	(33,134)
Cash flows from investing activities:
Purchase of property and equipment	(573)	(544)	(2,164)	(1,951)	(2,459)
Purchase of field equipment	(780)	(1,208)	(2,754)	(3,469)	(4,907)
Proceeds from maturity of short-term investments	45,000		150,000	120,000	120,000
Purchase of short-term investments	(44,652)		(148,786)	(104,006)	(104,006)
Net cash provided by (used in) investing activities	(1,005)	(1,752)	(3,704)	10,574	8,628
Cash flows from financing activities:
Proceeds from issuance of shares, net			938	781	1,540
Proceeds from long-term loan, net			149,150
Proceeds from other long-term loans				19	19
Repayment of long-term loan			(100,000)
Repayment of other long-term loan	(22)	(19)	(63)	(56)	(76)
Exercise of options and warrants	3,924	1,732	16,779	3,095	3,685
Net cash provided by (used in) financing activities	3,902	1,713	66,804	3,839	5,168
Effect of exchange rate changes on cash and cash equivalents	(2)	(2)	19	8	8
Increase (decrease) in cash, cash equivalents and restricted cash	8,533	2,506	44,440	(15,815)	(19,330)
Cash, cash equivalents and restricted cash at beginning of period	116,625	81,727	80,718	100,048	100,048
Cash, cash equivalents and restricted cash at the end of the period	125,158	84,233	125,158	84,233	80,718
Cash paid during the period for:
Income taxes	4,145	2,335	16,159	7,237	10,286
Interest	$ 3,454	$ 2,561	$ 9,879	$ 7,603	$ 10,162