Supplemental Consolidating Financial Information Condensed Statement of Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Net income (loss)	$ 59,588	$ 17,836	$ (5,038)	$ (6,767)
Unrealized foreign currency translation gains	0	(1)	2	15
Realized (gains) losses for foreign currency translation on business disposal reclassified into Other income (expense), net	(43)	0	559	252
Net other comprehensive income (loss) related to foreign currency translation	(43)	(1)	561	267
Unrealized gains (losses) on derivatives for the period	(2,270)	4,441	16,004	3,395
Derivative (gains) losses reclassified into Net sales	13,829	(1,020)	30,807	(2,047)
Derivative (gains) losses reclassified into Cost of sales	3,465	(61)	12,240	(236)
Net other comprehensive income (loss) related to derivatives	(12,634)	5,400	(2,563)	5,206
Actuarial gains (losses) for the period, net of tax	1,095	(563)	3,267	(905)
Amortization included in pension cost	315	296	599	596
Net other comprehensive income (loss) related to defined benefit pension and severance plans	1,410	(267)	3,866	(309)
Other comprehensive income (loss) of investments in subsidiaries	0	0	0	0
Comprehensive income (loss)	48,321	22,968	(3,174)	(1,603)
Reportable Legal Entities [Member] | Parent Company [Member]
Net income (loss)	59,588	17,836	(5,038)	(6,767)
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	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	(11,267)	5,132	1,864	5,164
Comprehensive income (loss)	48,321	22,968	(3,174)	(1,603)
Reportable Legal Entities [Member] | Subsidiary Issuer [Member]
Net income (loss)	42,393	31,394	45,814	30,956
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	0
Actuarial gains (losses) for the period, net of tax	1,112	(564)	1,112	(565)
Amortization included in pension cost	135	102	238	206
Net other comprehensive income (loss) related to defined benefit pension and severance plans	1,247	(462)	1,350	(359)
Other comprehensive income (loss) of investments in subsidiaries	(12,514)	5,594	514	5,523
Comprehensive income (loss)	31,126	36,526	47,678	36,120
Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member]
Net income (loss)	12,507	5,798	18,250	2,686
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	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)	12,507	5,798	18,250	2,686
Reportable Legal Entities [Member] | Non-Guarantor Subsidiaries [Member]
Net income (loss)	77,934	31,805	121,024	40,063
Unrealized foreign currency translation gains	0	(1)	2	15
Realized (gains) losses for foreign currency translation on business disposal reclassified into Other income (expense), net	(43)	0	559	252
Net other comprehensive income (loss) related to foreign currency translation	(43)	(1)	561	267
Unrealized gains (losses) on derivatives for the period	(2,270)	4,441	16,004	3,395
Derivative (gains) losses reclassified into Net sales	13,829	(1,020)	30,807	(2,047)
Derivative (gains) losses reclassified into Cost of sales	3,465	(61)	12,240	(236)
Net other comprehensive income (loss) related to derivatives	(12,634)	5,400	(2,563)	5,206
Actuarial gains (losses) for the period, net of tax	(17)	1	2,155	(340)
Amortization included in pension cost	180	194	361	390
Net other comprehensive income (loss) related to defined benefit pension and severance plans	163	195	2,516	50
Other comprehensive income (loss) of investments in subsidiaries	0	0	0	0
Comprehensive income (loss)	65,420	37,399	121,538	45,586
Consolidation, Eliminations [Member]
Net income (loss)	(132,834)	(68,997)	(185,088)	(73,705)
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	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	23,781	(10,726)	(2,378)	(10,687)
Comprehensive income (loss)	$ (109,053)	$ (79,723)	$ (187,466)	$ (84,392)