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Summary of Significant Accounting Policies (Tables) | 12 Months Ended
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Dec. 31, 2017
Accounting Policies [Abstract] |
Weighted-Average Useful Lives of Structures and Machinery and Equipment | The following table details the weighted-average useful lives of structures and machinery and equipment by reporting segment (numbers in years):
Segment | Structures | Machinery and equipment
Engineered Products and Solutions | 29 | 17
Global Rolled Products | 31 | 21
Transportation and Construction Solutions | 27 | 18
Weighted-Average Useful Lives of Software and Other Intangible Assets | The following table details the weighted-average useful lives of software and other intangible assets by reporting segment (numbers in years):
Segment | Software | Other intangible assets
Engineered Products and Solutions | 6 | 34
Global Rolled Products | 6 | 9
Transportation and Construction Solutions | 5 | 16

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