Summary of Disaggregated Revenue by Primary Geographical Market, Major Product Line and Timing (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Other Revenues [Line Items]
Licensing and related revenues	$ 10,083	$ 9,535
Royalties	7,486	11,752
Total	17,569	21,287
Transferred at Point in Time
Other Revenues [Line Items]
Licensing and related revenues	7,524
Royalties	7,486
Total	15,010
Transferred over Time
Other Revenues [Line Items]
Licensing and related revenues	2,559
Total	2,559
DSP Products
Other Revenues [Line Items]
Licensing and related revenues	7,375
Royalties	6,878
Total	14,253
Connectivity Products
Other Revenues [Line Items]
Licensing and related revenues	2,708
Royalties	608
Total	3,316
United States
Other Revenues [Line Items]
Licensing and related revenues	1,360
Royalties	347
Total	1,707	1,303
Europe and Middle East
Other Revenues [Line Items]
Licensing and related revenues	1,338
Royalties	1,115
Total	2,453	3,931
Asia Pacific
Other Revenues [Line Items]
Licensing and related revenues	7,385
Royalties	6,024
Total	$ 13,409	$ 16,053