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Summary of Business and Significant Accounting Policies (Tables) | 12 Months Ended
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Dec. 31, 2017
Accounting Policies [Abstract] |
Summary of Useful Lives Of Property and Equipment | The estimated useful lives for new property and equipment used for computing depreciation and amortizations are as follows:
| Years
Buildings |  |  | 39 |  |
Construction equipment | 5 |  | — |  | 15
Land improvements | 5 |  | — |  | 15
Office furniture and fixtures | 3 |  | — |  | 10
Leasehold improvements (or lease period, if shorter) | 3 |  | — |  | 10
Transportation equipment | 5 |  | — |  | 7

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- Definition The tabular disclosure of the useful lives of property, plant and equipment owned by the company. + References No definition available. + Details
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- References No definition available. + Details
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