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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, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |  |  |  |  |  |
Cost of Goods and Services Sold |  | $ 849,756 |  | $ 767,550 |  | $ 659,867
Income tax expense (benefit) | [1] | 11,526 |  | (53,163) |  | 3,217
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 |  | (665) |  | 1,229 |  | (1,568)
Income tax expense (benefit) |  | 253 |  | 287 |  | (579)
Total, net of tax |  | (918) |  | 942 |  | (989)
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 |  | (13,650) | [2] | (12,045) | [2] | (13,098)
Income tax expense (benefit) |  | (3,028) |  | (4,234) |  | (4,398)
Total, net of tax |  | (10,622) |  | (7,811) |  | (8,700)
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 and Services Sold |  | (1,069) |  | (1,210) |  | (1,630)
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 and Services Sold |  | (62) |  | (62) |  | $ 62
Selling, General and Administrative Expenses [Member] | 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 and Services Sold |  | $ (1,796) |  | $ (43) |  |
[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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