Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities:
Net income (loss)	$ (63,559)	$ (61,662)	$ (131,845)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	9,006	7,677	5,652
Asset write-downs and impairment of field equipment	407	241	6,446
Share-based compensation	39,846	27,116	22,139
Excess tax benefits from share-based award activity			(698)
Decrease (increase) in trade receivables, net	(4,151)	(23,228)	(6,339)
Amortization of discount, net	1,022	252	155
Decrease (increase) in receivables and prepaid expenses	(6,174)	1,979	243
Decrease (increase) in inventories	(529)	3,524	(11,955)
Decrease (increase) in other long-term assets	(949)	(554)	(692)
Increase (decrease) in trade payables	9,503	(1,150)	1,601
Increase (decrease) in other payables and accrued expenses	4,210	14,460	6,647
Increase (decrease) in employee benefit liabilities, net	133	440	97
Increase (decrease) in other long-term liabilities	9,370	(2,229)	957
Net cash provided by (used in) operating activities	(1,865)	(33,134)	(107,592)
Cash flows from investing activities:
Purchase of property and equipment	(2,916)	(2,459)	(5,673)
Purchase of field equipment	(3,795)	(4,907)	(11,990)
Proceeds from maturity of short-term investments	255,000	120,000	270,000
Purchase of short-term investments	(253,782)	(104,006)	(239,341)
Net cash provided by (used in) investing activities	(5,493)	8,628	12,996
Cash flows from financing activities:
Proceeds from issuance of shares, net	1,835	1,540	616
Proceeds from long-term loan, net	149,150		72,887
Repayment of long-term loan	(100,000)
Excess tax benefits from share-based award activity			698
Proceeds from issuance of other long-term loans		19
Repayment of other long-term loans	(84)	(76)	(70)
Exercise of options and warrants	18,468	3,685	993
Net cash provided by financing activities	69,369	5,168	75,124
Effect of exchange rate changes on cash and cash equivalents	27	8	10
Increase (decrease) in cash, cash equivalents and restricted cash	62,038	(19,330)	(19,462)
Cash, cash equivalents and restricted cash at the beginning of the year	80,718	100,048	119,510
Cash, cash equivalents and restricted cash at the end of the year	142,756	80,718	100,048
Cash paid during the year for:
Income taxes	20,350	10,286	9,447
Interest	$ 13,334	$ 10,162	$ 6,595