CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Cash flows from operating activities:
Net income (loss)	$ 9,284	$ 1,930	$ 14,891	$ (11,490)	$ (7,230)
Adjustments to reconcile net income (loss) to net cash used in operating activities:
Depreciation and amortization	2,188	1,932	6,677	5,993	8,460
Asset write-downs and impairment of field equipment	124	78	263	239	398
Share-based compensation	20,121	14,338	55,448	37,719	52,416
Foreign currency remeasurement loss (gain)	(79)	0	(549)	0	(917)
Decrease (increase) in accounts receivables	(7,678)	(9,986)	(33,556)	(17,020)	(36,496)
Amortization of discount (premium)	424	(547)	(654)	(1,712)	(2,176)
Decrease (increase) in inventories	(55)	1,067	(2,446)	(1,832)	(1,159)
Decrease (increase) in other long-term assets	(5,173)	1,069	(2,794)	1,151	3,446
Increase (decrease) in accounts payables and accrued expenses	9,908	6,433	7,974	10,902	16,883
Increase (decrease) in other long-term liabilities	1,905	(1,407)	413	(4,292)	(7,006)
Net cash provided by (used in) operating activities	30,969	14,907	45,667	19,658	26,620
Cash flows from investing activities:
Purchase of property, equipment and field equipment	(2,782)	(2,708)	(9,209)	(7,430)	(10,485)
Proceeds from maturity of short-term investments	150,000	105,000	150,000	315,661	420,661
Purchase of short-term investments	0	(104,466)	0	(313,142)	(461,843)
Net cash provided by (used in) investing activities	147,218	(2,174)	140,791	(4,911)	(51,667)
Cash flows from financing activities:
Proceeds from issuance of shares, net	0	0	1,667	1,208	2,467
Repayment of long-term loan	(150,007)	(7)	(150,022)	(23)	(31)
Exercise of options and warrants	9,514	15,475	17,710	51,910	59,245
Net cash provided by (used in) financing activities	(140,493)	15,468	(130,645)	53,095	61,681
Effect of exchange rate changes on cash, cash equivalents and restricted cash	102	(216)	152	(430)	26
Increase (decrease) in cash, cash equivalents and restricted cash	37,796	27,985	55,965	67,412	36,660
Cash, cash equivalents and restricted cash at the beginning of the period	197,585	182,183	179,416	142,756	142,756
Cash, cash equivalents and restricted cash at the end of the period	235,381	210,168	235,381	210,168	179,416
Cash paid during the period for:
Income taxes, net of refunds	4,382	3,040	11,319	10,431	11,241
Interest	1,840	3,453	8,671	10,247	13,699
Non-cash activities in accordance with ASC-842:
Right-of-use assets obtained in exchange for lease obligations	$ 675	$ 1,062	$ 2,849	$ 18,335	$ 22,943