Discontinued Operations - Results from Discontinued Operations (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Product and service revenues	$ 0	$ 0	$ 0
Total revenue	0	0	0
Cost of revenue	0	0	0
Research, development and other related costs	0	0	0
Selling, general and administrative	0	0	389
Restructuring, impairment of long-lived assets and other charges and gain on sale of patents	0	0	(371)
Impairment of goodwill	0	0	0
Total operating expenses	0	0	18
Other income and (expense), net	0	0	0
Operating loss before taxes	0	0	(18)
Expense (benefit) from income taxes	0	0	83
Net loss from discontinued operations	$ 0	$ 0	$ (101)