Supplemental Consolidating Financial Information Condensed Statement of Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Net income (loss)	$ 10,169	$ (17,956)	$ 5,131	$ (24,723)
Unrealized foreign currency translation gains	0	1	2	16
Realized (gains) losses for foreign currency translation on business disposal reclassified into Other income (expense), net	0	0	559	252
Net other comprehensive income (loss) related to foreign currency translation	0	1	561	268
Unrealized gains (losses) on derivatives for the period	(620)	19,072	15,384	22,467
Derivative (gains) losses reclassified into Net sales	7,876	1,543	38,683	(504)
Derivative (gains) losses reclassified into Cost of sales	3,760	822	16,000	586
Net other comprehensive income (loss) related to derivatives	(4,736)	18,351	(7,299)	23,557
Actuarial gains (losses) for the period, net of tax	(1)	0	3,266	(905)
Amortization included in pension cost	282	297	881	893
Net other comprehensive income (loss) related to defined benefit pension and severance plans	281	297	4,147	(12)
Other comprehensive income (loss) of investments in subsidiaries	0	0	0	0
Comprehensive income (loss)	5,714	693	2,540	(910)
Reportable Legal Entities [Member] | Parent Company [Member]
Net income (loss)	10,169	(17,956)	5,131	(24,723)
Unrealized foreign currency translation gains	0	0	0	0
Realized (gains) losses for foreign currency translation on business disposal reclassified into Other income (expense), net	0	0	0	0
Net other comprehensive income (loss) related to foreign currency translation	0	0	0	0
Unrealized gains (losses) on derivatives for the period	0	0	0	0
Derivative (gains) losses reclassified into Net sales	0	0	0	0
Derivative (gains) losses reclassified into Cost of sales	0	0	0	0
Net other comprehensive income (loss) related to derivatives	0		0	0
Actuarial gains (losses) for the period, net of tax	0	0	0	0
Amortization included in pension cost	0	0	0	0
Net other comprehensive income (loss) related to defined benefit pension and severance plans	0	0	0	0
Other comprehensive income (loss) of investments in subsidiaries	(4,455)	18,649	(2,591)	23,813
Comprehensive income (loss)	5,714	693	2,540	(910)
Reportable Legal Entities [Member] | Subsidiary Issuer [Member]
Net income (loss)	13,005	6,926	58,819	37,882
Unrealized foreign currency translation gains	0	0	0	0
Realized (gains) losses for foreign currency translation on business disposal reclassified into Other income (expense), net	0	0	0	0
Net other comprehensive income (loss) related to foreign currency translation	0	0	0	0
Unrealized gains (losses) on derivatives for the period	0	0	0	0
Derivative (gains) losses reclassified into Net sales	0	0	0	0
Derivative (gains) losses reclassified into Cost of sales	0	0	0	0
Net other comprehensive income (loss) related to derivatives	0		0	0
Actuarial gains (losses) for the period, net of tax	1	1	1,112	(564)
Amortization included in pension cost	102	102	340	308
Net other comprehensive income (loss) related to defined benefit pension and severance plans	103	103	1,452	(256)
Other comprehensive income (loss) of investments in subsidiaries	(4,558)	18,546	(4,043)	24,069
Comprehensive income (loss)	8,550	25,575	56,228	61,695
Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member]
Net income (loss)	8,900	2,675	27,150	5,361
Unrealized foreign currency translation gains	0	0	0	0
Realized (gains) losses for foreign currency translation on business disposal reclassified into Other income (expense), net	0	0	0	0
Net other comprehensive income (loss) related to foreign currency translation	0	0	0	0
Unrealized gains (losses) on derivatives for the period	0	0	0	0
Derivative (gains) losses reclassified into Net sales	0	0	0	0
Derivative (gains) losses reclassified into Cost of sales	0	0	0	0
Net other comprehensive income (loss) related to derivatives	0		0	0
Actuarial gains (losses) for the period, net of tax	0	0	0	0
Amortization included in pension cost	0	0	0	0
Net other comprehensive income (loss) related to defined benefit pension and severance plans	0	0	0	0
Other comprehensive income (loss) of investments in subsidiaries	0	0	0	0
Comprehensive income (loss)	8,900	2,675	27,150	5,361
Reportable Legal Entities [Member] | Non-Guarantor Subsidiaries [Member]
Net income (loss)	29,228	4,226	150,252	44,289
Unrealized foreign currency translation gains	0	1	2	16
Realized (gains) losses for foreign currency translation on business disposal reclassified into Other income (expense), net	0	0	559	252
Net other comprehensive income (loss) related to foreign currency translation	0	1	561	268
Unrealized gains (losses) on derivatives for the period	(620)	19,072	15,384	22,467
Derivative (gains) losses reclassified into Net sales	7,876	1,543	38,683	(504)
Derivative (gains) losses reclassified into Cost of sales	3,760	822	16,000	586
Net other comprehensive income (loss) related to derivatives	(4,736)		(7,299)	23,557
Actuarial gains (losses) for the period, net of tax	(2)	(1)	2,154	(341)
Amortization included in pension cost	180	195	541	585
Net other comprehensive income (loss) related to defined benefit pension and severance plans	178	194	2,695	244
Other comprehensive income (loss) of investments in subsidiaries	0	0	0	0
Comprehensive income (loss)	24,670	22,772	146,209	68,358
Consolidation, Eliminations [Member]
Net income (loss)	(51,133)	(13,827)	(236,221)	(87,532)
Unrealized foreign currency translation gains	0	0	0	0
Realized (gains) losses for foreign currency translation on business disposal reclassified into Other income (expense), net	0		0	0
Net other comprehensive income (loss) related to foreign currency translation	0	0	0	0
Unrealized gains (losses) on derivatives for the period	0	0	0	0
Derivative (gains) losses reclassified into Net sales	0	0	0	0
Derivative (gains) losses reclassified into Cost of sales	0	0	0	0
Net other comprehensive income (loss) related to derivatives	0		0	0
Actuarial gains (losses) for the period, net of tax	0	0	0	0
Amortization included in pension cost	0	0	0	0
Net other comprehensive income (loss) related to defined benefit pension and severance plans	0	0	0	0
Other comprehensive income (loss) of investments in subsidiaries	9,013	(37,195)	6,634	(47,882)
Comprehensive income (loss)	$ (42,120)	$ (51,022)	$ (229,587)	$ (135,414)