CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Cash flows from operating activities:
Net income (loss)	$ 1,655	$ (1,270)	$ 5,607	$ (13,420)	$ (7,230)
Adjustments to reconcile net income (loss) to net cash used in operating activities:
Depreciation and amortization	2,601	2,132	4,489	4,061	8,460
Asset write-downs and impairment of field equipment	133	86	139	161	398
Share-based compensation	18,770	13,732	35,327	23,381	52,416
Foreign currency remeasurement loss (gain)	(463)	0	(470)	0	(917)
Decrease (increase) in accounts receivables	(6,160)	(4,998)	(25,878)	(7,034)	(36,496)
Amortization of discount (premium)	(538)	(587)	(1,078)	(1,165)	(2,176)
Decrease (increase) in inventories	(3,539)	(1,316)	(2,391)	(2,899)	(1,159)
Decrease (increase) in other long-term assets	1,143	168	2,379	82	3,446
Increase (decrease) in accounts payables and accrued expenses	405	2,223	(1,934)	4,469	16,883
Increase (decrease) in other long-term liabilities	(1,266)	(1,104)	(1,492)	(2,885)	(7,006)
Net cash provided by (used in) operating activities	12,741	9,066	14,698	4,751	26,620
Cash flows from investing activities:
Purchase of property, equipment and field equipment	(3,315)	(2,397)	(6,427)	(4,722)	(10,485)
Proceeds from maturity of short-term investments	0	105,000	0	210,661	420,661
Purchase of short-term investments	0	(104,351)	0	(208,676)	(461,843)
Net cash provided by (used in) investing activities	(3,315)	(1,748)	(6,427)	(2,737)	(51,667)
Cash flows from financing activities:
Proceeds from issuance of shares, net	1,667	1,208	1,667	1,208	2,467
Repayment of long-term loan	(7)	(8)	(15)	(16)	(31)
Exercise of options and warrants	3,685	19,457	8,196	36,435	59,245
Net cash provided by (used in) financing activities	5,345	20,657	9,848	37,627	61,681
Effect of exchange rate changes on cash, cash equivalents and restricted cash	109	47	50	(214)	26
Increase (decrease) in cash, cash equivalents and restricted cash	14,880	28,022	18,169	39,427	36,660
Cash, cash equivalents and restricted cash at the beginning of the period	182,705	154,161	179,416	142,756	142,756
Cash, cash equivalents and restricted cash at the end of the period	197,585	182,183	197,585	182,183	179,416
Cash paid during the period for:
Income taxes	4,728	4,358	6,937	7,391	11,241
Interest	3,415	3,415	6,831	6,794	13,699
Non-cash activities in accordance with ASC-842:
Right-of-use assets obtained in exchange for lease obligations	$ 1,391	$ 1,539	$ 2,174	$ 17,273	$ 22,943