Pension and Severance Plans (Korean Severance Plan) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Deferred Compensation Liability, Current and Noncurrent [Roll Forward]
Total severance obligation balance at the end of year	$ 136,214	$ 142,959	$ 146,661
Less current portion of accrued severance obligation (Note 12)	14,053	14,306	13,226
Non-current portion of severance obligation	122,161	128,653	133,435
Korean Severance Plan [Member]
Deferred Compensation Liability, Current and Noncurrent [Roll Forward]
Balance at the beginning of year	143,151	146,880	145,373
Provision of severance benefits	6,746	21,088	17,593
Severance payments	(9,429)	(15,021)	(10,160)
(Gain) loss on foreign currency	(4,072)	(9,796)	(5,926)
Balance at the end of year	136,396	143,151	146,880
Payments remaining with the National Pension Fund	$ (182)	$ (192)	$ (219)