Geographic and Segment Information - Net Sales by Region, Based on Location of Customer (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Revenues from External Customers and Long-Lived Assets [Line Items]
Total net sales	$ 194,332	$ 170,812	$ 530,566	$ 558,667
Korea [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total net sales	84,763	74,060	219,096	239,081
Asia Pacific (other than Korea) [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total net sales	80,123	68,496	224,681	209,219
U.S.A. [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total net sales	25,079	22,786	69,428	78,536
Europe [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total net sales	3,829	4,504	16,323	29,100
Others [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total net sales	$ 538	$ 966	$ 1,038	$ 2,731