Geographic and Other Information - Net Sales by Region, Based on Location of Products are Billed (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	$ 124,813	$ 149,167	$ 364,114	$ 397,319
Standard products business [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	116,262	139,273	335,953	371,543
Standard products business [Member] | Korea [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	28,370	36,114	81,144	107,319
Standard products business [Member] | Asia Pacific (Other Than Korea) [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	84,188	100,872	245,940	258,276
Standard products business [Member] | United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	1,789	482	3,959	1,600
Standard products business [Member] | Europe [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	1,451	1,501	3,278	3,515
Standard products business [Member] | Others [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	$ 464	$ 304	$ 1,632	$ 833