Revenues - Adoption of ASC 606 (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Jan. 01, 2018	Dec. 31, 2017
Balance Sheet
Receivables, net	$ 1,087		$ 1,087		$ 1,452	$ 1,113
Deferred tax assets	38,517		38,517		37,772	38,661
Other long-term assets	2,043		2,043		1,986	2,308
Billings in excess of costs on uncompleted contracts	0		0		0	1,830
Other current liabilities	1,100		1,100		2,673	2,664
Other long-term liabilities	293		293		285	2,285
Retained earnings (deficit)	10,425		10,425		(12,528)	(15,478)
Statement of Operations
Total revenues	4,273	$ 27,331	8,172	$ 36,475
Operating expenses:
Total operating expenses	5,842	27,315	11,453	38,415
Operating loss	(1,569)	16	(3,281)	(1,940)
Other income (expense):
Royalties, related party	0		0
Total other income (expense)	15,511	10,034	27,454	26,064
Income before income tax expense	13,942	10,050	24,173	24,124
Equipment sales
Statement of Operations
Total revenues	24	24,619	72	29,727
Operating expenses:
Equipment sales cost of revenue	(198)	22,650	(346)	26,793
License royalties, related party
Statement of Operations
Total revenues	3,523	$ 1,866	6,753	$ 3,621
Calculated under Revenue Guidance in Effect before Topic 606
Balance Sheet
Receivables, net						1,113
Deferred tax assets						38,661
Other long-term assets						2,308
Billings in excess of costs on uncompleted contracts						1,830
Other current liabilities						2,664
Other long-term liabilities						2,285
Retained earnings (deficit)						$ (15,478)
Calculated under Revenue Guidance in Effect before Topic 606 | ASU No. 2014-09
Balance Sheet
Receivables, net	(159)		(159)
Deferred tax assets	889		889
Other long-term assets	322		322
Billings in excess of costs on uncompleted contracts	2,009		2,009
Other current liabilities	0		0
Other long-term liabilities	2,000		2,000
Retained earnings (deficit)	(2,957)		(2,957)
Statement of Operations
Total revenues	4,009		779
Operating expenses:
Total operating expenses	7,525		7,525
Operating loss	(3,516)		(6,746)
Other income (expense):
Royalties, related party	3,523		6,753
Total other income (expense)	3,523		6,753
Income before income tax expense	7		7
Calculated under Revenue Guidance in Effect before Topic 606 | ASU No. 2014-09 | Equipment sales
Statement of Operations
Total revenues	7,532		7,532
Operating expenses:
Equipment sales cost of revenue	7,525		7,525
Calculated under Revenue Guidance in Effect before Topic 606 | ASU No. 2014-09 | License royalties, related party
Statement of Operations
Total revenues	(3,523)		(6,753)
Difference between Revenue Guidance in Effect before and after Topic 606
Balance Sheet
Receivables, net	928		928
Deferred tax assets	39,406		39,406
Other long-term assets	2,365		2,365
Billings in excess of costs on uncompleted contracts	2,009		2,009
Other current liabilities	1,100		1,100
Other long-term liabilities	2,293		2,293
Retained earnings (deficit)	7,468		7,468
Statement of Operations
Total revenues	8,282		8,951
Operating expenses:
Total operating expenses	13,367		18,978
Operating loss	(5,085)		(10,027)
Other income (expense):
Royalties, related party	3,523		6,753
Total other income (expense)	19,034		34,207
Income before income tax expense	13,949		24,180
Difference between Revenue Guidance in Effect before and after Topic 606 | Equipment sales
Statement of Operations
Total revenues	7,556		7,604
Operating expenses:
Equipment sales cost of revenue	7,327		7,179
Difference between Revenue Guidance in Effect before and after Topic 606 | License royalties, related party
Statement of Operations
Total revenues	$ 0		$ 0
Difference between Revenue Guidance in Effect before and after Topic 606 | ASU No. 2014-09
Balance Sheet
Receivables, net					339
Deferred tax assets					(889)
Other long-term assets					(322)
Billings in excess of costs on uncompleted contracts					(1,830)
Other current liabilities					9
Other long-term liabilities					(2,000)
Retained earnings (deficit)					$ 2,950