Segment And Geographic Information - Schedule of Geographic Revenue Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues from External Customers and Long-Lived Assets [Line Items]
Foreign revenues	$ 373,732	$ 259,565	$ 273,300
Percentage of revenue (or more)	100.00%	100.00%	100.00%
Two Customers
Revenues from External Customers and Long-Lived Assets [Line Items]
Percentage of revenue (or more)	10.00%
Four Customers
Revenues from External Customers and Long-Lived Assets [Line Items]
Percentage of revenue (or more)		10.00%	10.00%
U.S.
Revenues from External Customers and Long-Lived Assets [Line Items]
Foreign revenues	$ 164,846	$ 99,594	$ 98,428
Percentage of revenue (or more)	44.00%	38.00%	36.00%
Japan
Revenues from External Customers and Long-Lived Assets [Line Items]
Foreign revenues	$ 81,688	$ 6,866	$ 9,409
Percentage of revenue (or more)	22.00%	3.00%	3.00%
Korea
Revenues from External Customers and Long-Lived Assets [Line Items]
Foreign revenues	$ 50,155	$ 95,170	$ 87,527
Percentage of revenue (or more)	13.00%	37.00%	32.00%
Taiwan
Revenues from External Customers and Long-Lived Assets [Line Items]
Foreign revenues	$ 33,861	$ 34,763	$ 57,049
Percentage of revenue (or more)	9.00%	13.00%	21.00%
Other Geographical Area
Revenues from External Customers and Long-Lived Assets [Line Items]
Foreign revenues	$ 43,182	$ 23,172	$ 20,887
Percentage of revenue (or more)	12.00%	9.00%	8.00%