Accrued Severance Benefits - Changes in Accrued Severance Benefits (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Postemployment Benefits [Abstract]
Beginning balance	$ 145,598	$ 136,176	$ 140,405	$ 135,356
Provisions	4,617	5,392	11,877	9,426
Severance payments	(2,890)	(1,976)	(4,231)	(3,490)
Translation adjustments	(2,525)	7,331	(3,251)	5,631
Ending balance	144,800	146,923	144,800	146,923
Less: Cumulative contributions to the National Pension Fund	(333)	(387)	(333)	(387)
Group severance insurance plan	(740)	(825)	(740)	(825)
Accrued severance benefits, net	$ 143,727	$ 145,711	$ 143,727	$ 145,711	$ 139,289