CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Cash flows from operating activities:
Net loss	$ (21,174)	$ (40,612)	$ (39,219)	$ (76,049)	$ (131,845)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,811	1,407	3,471	2,510	5,652
Asset write-downs and impairment of field equipment	59	6,425	134	6,430	6,446
Increase in accrued interest expense		(637)
Share-based compensation to employees	7,570	5,637	12,131	11,093	22,139
Excess tax benefits from share-based award activity					(698)
Increase in trade receivables	(2,064)		(7,550)		(6,339)
Amortization of discount (premium)	103	(39)	209	(56)	155
Decrease (increase) in receivables and prepaid expenses	3,354	(1,672)	(1,461)	(2,208)	243
Decrease (Increase) in inventories	803	(4,769)	403	(7,621)	(11,955)
Increase in other long-term assets	(38)	(111)	(294)	(278)	(692)
Increase (decrease) in trade payables	(1,638)	2,321	(5,195)	4,144	1,601
Increase in other payables and accrued expenses	4,888	2,399	3,478	756	6,647
Increase in employee benefit liabilities, net	130	32	239	270	97
Increase in other long-term liabilities	321	225	871	638	957
Net cash used in operating activities	(5,875)	(29,394)	(32,783)	(60,371)	(107,592)
Cash flows from investing activities:
Purchase of property and equipment	(376)	(2,338)	(1,407)	(3,340)	(5,674)
Purchase of field equipment	(859)	(4,274)	(2,261)	(6,100)	(11,990)
increase in restricted cash	(1)	(13)	(1,269)	(12)	(180)
Proceeds from maturity of short-term investments	60,000		120,000	150,000	270,000
Purchase of short-term investments	(59,352)		(104,006)	(119,728)	(239,341)
Net cash provided by (used in) investing activities	(588)	(6,625)	11,057	20,820	12,815
Cash flows from financing activities:
Proceeds from issuance of shares, net	781		781		616
Proceeds from long-term loan, net	19	17	19	17	72,887
Excess tax benefits from share-based award activity					698
Repayment of other long-term loan	(19)	(19)	(37)	(35)	(70)
Exercise of options and warrants	1,286	904	1,363	961	993
Net cash provided by financing activities	2,067	902	2,126	943	75,124
Effect of exchange rate changes on cash and cash equivalents	(1)	56	10	56	10
Decrease in cash and cash equivalents	(4,397)	(35,061)	(19,590)	(38,552)	(19,643)
Cash and cash equivalents at the beginning of the period	84,587	115,932	99,780	119,423	119,423
Cash and cash equivalents at the end of the period	80,190	80,871	80,190	80,871	99,780
Cash paid during the period for:
Income taxes	1,500	1,587	4,902	3,169	9,447
Interest	$ 2,533	$ 1,269	$ 5,041	$ 1,933	$ 6,595