Summary of Significant Accounting Policies (Tables)

12 Months Ended

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