Goodwill and Other Intangible Assets	12 Months Ended
Goodwill and Other Intangible Assets	Dec. 31, 2017
Goodwill and Other Intangible Assets [Abstract]
Goodwill and Other Intangible Assets	4. Goodwill and Other Intangible Assets As of December 31, 2017, 2016 and 2015, the Company had $585.0 million of goodwill allocated to its reporting units as follows: Civil, $415.3 million; Building, $13.5 million; and Specialty Contractors, $156.2 million. The balances presented include historical accumulated impairment of $76.7 million for the Civil segment and $411.3 million for the Building segment. In addition, as of December 31, 2017 and 2016, the Company had the following: (1) non-amortizable trade names with a carrying value of $50.4 million; (2) amortizable trade names with a gross carrying value of $51.1 million and accumulated amortization as of December 31, 2017 and 2016 of $16.3 million and $13.8 million, respectively; and (3) amortizable customer relationships with a gross carrying value of $23.2 million and accumulated amortization as of December 31, 2017 and 2016 of $18.9 million and $17.9 million, respectively. Amortization expense related to amortizable intangible assets for the years ended December 31, 2017, 2016 and 2015 totaled $3.5 million, $3.5 million and $3.7 million, respectively. Future amortization expense related to amortizable intangible assets will be approximately $3.5 million per year for the years 2018 through 2021 and $2.6 million for the year 2022. The weighted-average amortization period for amortizable trade names and customer relationships is 20 years and 12 years, respectively.

The entire disclosure for the aggregate amount of goodwill and a description of intangible assets, which may include (a) for amortizable intangible assets (also referred to as finite-lived intangible assets), the carrying amount, the amount of any significant residual value, and the weighted-average amortization period, (b) for intangible assets not subject to amortization (also referred to as indefinite-lived intangible assets), the carrying amount, and (c) the amount of research and development assets acquired and written off in the period, including the line item in the income statement in which the amounts written off are aggregated, if not readily apparent from the income statement. Also discloses (a) for amortizable intangibles assets in total and by major class, the gross carrying amount and accumulated amortization, the total amortization expense for the period, and the estimated aggregate amortization expense for each of the five succeeding fiscal years, (b) for intangible assets not subject to amortization the carrying amount in total and by major class, and (c) for goodwill, in total and for each reportable segment, the changes in the carrying amount of goodwill during the period (including the aggregate amount of goodwill acquired, the aggregate amount of impairment losses recognized, and the amount of goodwill included in the gain (loss) on disposal of a reporting unit). If any part of goodwill has not been allocated to a reportable segment, discloses the unallocated amount and the reasons for not allocating. For each impairment loss recognized related to an intangible asset (excluding goodwill), discloses: (a) a description of the impaired intangible asset and the facts and circumstances leading to the impairment, (b) the amount of the impairment loss and the method for determining fair value, (c) the caption in the income statement or the statement of activities in which the impairment loss is aggregated, and (d) the segment in which the impaired intangible asset is reported. For each goodwill impairment loss recognized, discloses: (a) a description of the facts and circumstances leading to the impairment, (b) the amount of the impairment loss and the method of determining the fair value of the associated reporting unit, and (c) if a recognized impairment loss is an estimate not finalized and the reasons why the estimate is not final. May also disclose the nature and amount of any significant adjustments made to a previous estimate of an impairment loss.