Geographic and Segment Information - Net Sales by Region, Based on Location of Customer (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenues from External Customers and Long-Lived Assets [Line Items]
Total net sales	$ 167,652	$ 194,332	$ 172,070	$ 164,164	$ 175,510	$ 170,812	$ 193,533	$ 194,322	$ 698,218	$ 734,177	$ 807,336
Korea [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total net sales									260,139	313,634	365,682
Asia Pacific (other than Korea) [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total net sales									324,248	284,429	271,908
U.S.A. [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total net sales									91,308	100,790	124,481
Europe [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total net sales									21,159	32,136	39,304
Others [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total net sales									$ 1,364	$ 3,188	$ 5,961