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Summary of Significant Accounting Policies (Schedule of Reclassifications Out of AOCI) (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |  |  |  |  |  |
Cost of goods sold |  | $ (775,628) |  | $ (668,626) |  | $ (725,459)
Income tax expense (benefit) | [1] | (53,163) |  | 3,217 |  | 8,928
Gain (loss) on derivative financial instruments | Reclassification out of Accumulated Other Comprehensive Income |  |  |  |  |  |
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |  |  |  |  |  |
Total, before taxes |  | 1,229 |  | (1,568) |  | (3,476)
Income tax expense (benefit) |  | 287 |  | (579) |  | (1,284)
Total, net of tax |  | 942 |  | (989) |  | (2,192)
Pension and other post-retirement benefit adjustments | Reclassification out of Accumulated Other Comprehensive Income |  |  |  |  |  |
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |  |  |  |  |  |
Actuarial gain (loss) and prior service costs, before taxes |  | (12,045) | [2] | (13,098) | [2] | (16,041)
Income tax expense (benefit) |  | (4,234) |  | (4,398) |  | (5,823)
Total, net of tax |  | (7,811) |  | (8,700) |  | (10,218)
Aluminum Futures Contracts | Gain (loss) on derivative financial instruments | Reclassification out of Accumulated Other Comprehensive Income |  |  |  |  |  |
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |  |  |  |  |  |
Cost of goods sold |  | 1,210 |  | (1,630) |  | 3,538
Foreign Currency Forward Contracts | Gain (loss) on derivative financial instruments | Reclassification out of Accumulated Other Comprehensive Income |  |  |  |  |  |
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |  |  |  |  |  |
Cost of goods sold |  | $ 62 |  | $ 62 |  | $ (62)
[1] | See Notes 1, 3, 4 and 17 for more information on losses associated with plant shutdowns, asset impairments and restructurings, unusual items, gains or losses from sale of assets, gains or losses on an investment accounted for under the fair value method and other items.
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- Definition Total costs related to goods produced and sold during the reporting period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.2(a)) -URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688 + Details
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