Geographic and Segment Information - Net Sales by Region, Based on Location of Customer (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Revenues from External Customers and Long-Lived Assets [Line Items]
Total net sales	$ 172,070	$ 193,533	$ 336,234	$ 387,855
Korea [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total net sales	67,320	80,575	134,333	165,021
Asia Pacific (other than Korea) [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total net sales	74,337	72,212	144,558	140,723
U.S.A. [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total net sales	24,596	27,060	44,349	55,750
Europe [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total net sales	5,601	12,867	12,494	24,596
Others [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total net sales	$ 216	$ 819	$ 500	$ 1,765