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Segment, Customer Concentration and Geographical Information - Revenues Generated by Each Business Unit (Detail) - USD ($) $ 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
Revenue from External Customer [Line Items]
Total revenues	$ 7,352	$ 6,525	$ 6,945	$ 5,463	$ 5,732	$ 5,804	$ 5,862	$ 5,576	$ 26,285	$ 22,974
Cost of revenues									4,333	5,082
Gross profit	$ 6,424	$ 5,546	$ 5,829	$ 4,154	$ 4,377	$ 4,645	$ 4,577	$ 4,293	21,952	17,892
Wireless [Member]
Revenue from External Customer [Line Items]
Total revenues									24,474	18,342
Graphics [Member]
Revenue from External Customer [Line Items]
Total revenues									$ 1,811	$ 4,632