CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Cash flows from operating activities:
Net loss	$ (18,045)	$ (35,437)	$ (131,845)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,660	1,103	5,652
Asset write-downs and impairment of field equipment	75	5	6,446
Increase in accrued interest expense		637
Share-based compensation to employees	4,561	5,456	22,139
Excess tax benefits from share-based award activity			(698)
Increase in trade receivables	(5,486)		(6,339)
Amortization of discount (premium)	106	(17)	155
Decrease (increase) in receivables and prepaid expenses	(4,815)	(536)	243
Increase in inventories	(400)	(2,852)	(11,955)
Increase in other long-term assets	(256)	(167)	(692)
Increase (decrease) in trade payables	(3,557)	1,823	1,601
Increase (decrease) in other payables and accrued expenses	(1,410)	(1,643)	6,647
Increase in employee benefit liabilities, net	109	238	97
Increase in other long-term liabilities	550	413	957
Net cash used in operating activities	(26,908)	(30,977)	(107,592)
Cash flows from investing activities:
Purchase of property and equipment	(1,031)	(1,002)	(5,674)
Purchase of field equipment	(1,402)	(1,826)	(11,990)
Decrease (increase) in restricted cash	(1,268)	1	(180)
Proceeds from maturity of short-term investments	60,000	150,000	270,000
Purchase of short-term investments	(44,654)	(119,728)	(239,341)
Net cash provided by investing activities	11,645	27,445	12,815
Cash flows from financing activities:
Proceeds from issuance of shares, net			616
Proceeds from long-term loan, net			72,887
Excess tax benefits from share-based award activity			698
Repayment of other long-term loan	(18)	(16)	(70)
Exercise of options and warrants	77	57	993
Net cash provided by financing activities	59	41	75,124
Effect of exchange rate changes on cash and cash equivalents	11		10
Decrease in cash and cash equivalents	(15,193)	(3,491)	(19,643)
Cash and cash equivalents at the beginning of the period	99,780	119,423	119,423
Cash and cash equivalents at the end of the period	84,587	115,932	99,780
Cash paid during the period for:
Income taxes	3,402	1,582	9,447
Interest	$ 2,508	$ 664	$ 6,595