Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2018

Accounting Policies [Abstract]

Summary of restricted cash

	As of December 31,
	2018		2017
	(in thousands)
Certificates of deposit	$	—	$	5
Flexible spending funds		—		3
Fixed deposit pledge		169		173
	$	169	$	181

Summary of share repurchase activity

Periods	Total number of shares purchased		Average price paid per share		Total number of shares purchased as part of publicly announced program		Approximate dollar value of shares that may yet be purchased under the program (in thousands)
December 1, 2018, to December 31, 2018		8,457	$	7.69		8,457		2,935
Total		8,457					$	2,935

Schedule of allowance for doubtful accounts

	Year ended December 31,
	2018		2017
	(in thousands)
Beginning balance	$	7	$	31
Charges to costs and expenses		—		(20	)
Account write-offs, less recoveries		—		(4	)
Ending balance	$	7	$	7

Schedule of inventories

	As of December 31,
	2018		2017
	(in thousands)
Raw materials	$	468	$	476
Work-in-process		1,322		2,334
Finished goods		340		220
	$	2,130	$	3,030

Schedule of property and equipment

	As of December 31,
	2018			2017
	(in thousands)
Machinery, equipment and tooling	$	3,293		$	6,105
Buildings		1,686			—
Information systems		819			819
Land and land improvements		594			—
Furniture and fixtures		8			8
Leasehold improvements		—			4,624
Total cost		6,400			11,556
Accumulated depreciation and amortization		(3,672	)		(10,741	)
Property and equipment, net	$	2,728		$	815

Schedule of property and equipment, estimated useful lives

Asset description	Life
Buildings	39 years
Machinery, equipment and tooling	3-10 years
Leasehold improvements	Lesser of life of lease or economic life
Furniture and fixtures	7 years
Information systems	3 years

Schedule of product warranty liability

	Year ended December 31,
	2018			2017
	(in thousands)
Balance, beginning of period	$	15		$	27
Charged to cost of sales		23			20
Actual product warranty expenditures		(30	)		(32	)
Balance, end of period	$	8		$	15

Summary of accumulated comprehensive loss

	Year ended December 31,
	2018			2017
	(in thousands)
Unrealized loss on investments, net of tax	$	(1	)	$	(2	)
Unrealized loss on currency translation		(1	)		(1	)
Ending balance	$	(2	)	$	(3	)