New Revenue Recognition Standard - Condensed Consolidated Statement of Operations (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues:
Total revenues	$ 29,402	$ 25,268	$ 24,168	$ 30,495	$ 28,570	$ 36,395	$ 34,301	$ 29,101	$ 109,333	$ 128,367	$ 146,444
Loss from Operations	(42,578)	(29,024)	(34,311)	(25,264)	(41,088)	(15,054)	(18,609)	(21,909)	(131,177)	(96,660)	(62,886)
Loss before income taxes									(120,010)	(108,026)	(72,083)
Net loss	$ (49,221)	$ (68,718)	$ 13,744	$ (15,816)	$ (28,556)	$ (18,293)	$ (20,852)	$ (23,547)	$ (120,011)	$ (91,248)	$ (69,770)
Net income per share:
Basic ($ per share)									$ (1.16)	$ (1.07)	$ (0.96)
Diluted ($ per share)									$ (1.16)	$ (1.07)	$ (0.96)
Weighted average shares outstanding:
Basic (shares)									103,305,911	85,115,592	72,824,070
Diluted (shares)									103,305,911	85,115,592	72,824,070
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Accounting Standards Update 2014-09 [Member]
Revenues:
Total revenues									$ 1,085
Loss from Operations									1,085
Loss before income taxes									1,085
Net loss									$ 1,085
Net income per share:
Basic ($ per share)									$ 0.01
Diluted ($ per share)									$ 0.01
Weighted average shares outstanding:
Basic (shares)									103,305,911
Diluted (shares)									103,305,911
Calculated under Revenue Guidance in Effect before Topic 606 [Member]
Revenues:
Total revenues									$ 110,418
Loss from Operations									(130,092)
Loss before income taxes									(118,925)
Net loss									$ (118,926)
Net income per share:
Basic ($ per share)									$ (1.15)
Diluted ($ per share)									$ (1.15)
Weighted average shares outstanding:
Basic (shares)									103,305,911
Diluted (shares)									103,305,911
Product [Member]
Revenues:
Total revenues									$ 104,466	$ 116,178	$ 128,596
Product [Member] | Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Accounting Standards Update 2014-09 [Member]
Revenues:
Total revenues									906
Product [Member] | Calculated under Revenue Guidance in Effect before Topic 606 [Member]
Revenues:
Total revenues									105,372
License and Service [Member]
Revenues:
Total revenues									4,867	$ 12,189	$ 17,848
License and Service [Member] | Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Accounting Standards Update 2014-09 [Member]
Revenues:
Total revenues									179
License and Service [Member] | Calculated under Revenue Guidance in Effect before Topic 606 [Member]
Revenues:
Total revenues									$ 5,046