Revenue Recognition - Summary of Net Revenues Disaggregated by Category (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Disaggregation of Revenue [Line Items]
Revenue	$ 74,196	$ 57,709	$ 139,465	$ 112,171
Direct Customers, Contract Manufacturers and Non-stocking Distributors [Member]
Disaggregation of Revenue [Line Items]
Revenue	66,534		123,294
Stocking Distributors, Net of Sales Allowances [Member]
Disaggregation of Revenue [Line Items]
Revenue	6,943		14,849
Non-recurring Engineering [Member]
Disaggregation of Revenue [Line Items]
Revenue	662		1,172
Royalties [Member]
Disaggregation of Revenue [Line Items]
Revenue	39		114
Other [Member]
Disaggregation of Revenue [Line Items]
Revenue	18		36
BBU [Member]
Disaggregation of Revenue [Line Items]
Revenue	48,349		88,986
BBU [Member] | Direct Customers, Contract Manufacturers and Non-stocking Distributors [Member]
Disaggregation of Revenue [Line Items]
Revenue	43,404		78,878
BBU [Member] | Stocking Distributors, Net of Sales Allowances [Member]
Disaggregation of Revenue [Line Items]
Revenue	4,735		9,698
BBU [Member] | Non-recurring Engineering [Member]
Disaggregation of Revenue [Line Items]
Revenue	197		372
BBU [Member] | Royalties [Member]
Disaggregation of Revenue [Line Items]
Revenue	13		38
VI Chip [Member]
Disaggregation of Revenue [Line Items]
Revenue	19,890		40,029
VI Chip [Member] | Direct Customers, Contract Manufacturers and Non-stocking Distributors [Member]
Disaggregation of Revenue [Line Items]
Revenue	17,628		34,934
VI Chip [Member] | Stocking Distributors, Net of Sales Allowances [Member]
Disaggregation of Revenue [Line Items]
Revenue	1,865		4,419
VI Chip [Member] | Non-recurring Engineering [Member]
Disaggregation of Revenue [Line Items]
Revenue	375		620
VI Chip [Member] | Royalties [Member]
Disaggregation of Revenue [Line Items]
Revenue	13		38
VI Chip [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue	9		18
Picor [Member]
Disaggregation of Revenue [Line Items]
Revenue	5,957		10,450
Picor [Member] | Direct Customers, Contract Manufacturers and Non-stocking Distributors [Member]
Disaggregation of Revenue [Line Items]
Revenue	5,502		9,482
Picor [Member] | Stocking Distributors, Net of Sales Allowances [Member]
Disaggregation of Revenue [Line Items]
Revenue	343		732
Picor [Member] | Non-recurring Engineering [Member]
Disaggregation of Revenue [Line Items]
Revenue	90		180
Picor [Member] | Royalties [Member]
Disaggregation of Revenue [Line Items]
Revenue	13		38
Picor [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue	$ 9		$ 18