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Summary of Business and Significant Accounting Policies - Narrative (Details) | 12 Months Ended
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Dec. 31, 2017 USD ($) reporting_unit segment | Dec. 31, 2016 USD ($) | Dec. 31, 2015 USD ($)
Financing Receivable, Impaired [Line Items] |  |  |
Ownership interest in joint venture, entity is consolidated | 50.00% |  |
Contract receivable retainage | $ 43,500,000 | $ 23,400,000 |
Unbilled contracts receivable | 0 | 0 |
Provision for doubtful accounts | 0 | 0 | $ 0
Allowance for doubtful accounts | 0 | 0 |
Inventories | 4,621,000 | 3,708,000 |
Depreciation | 15,100,000 | 15,700,000 | 16,200,000
Capital lease obligations | 300,000 | 400,000 |
Impairment of long-lived assets | $ 0 | 0 | 0
Number of reportable segments | segment | 2 |  |
Number of reporting units | reporting_unit | 2 |  |
Costs and Estimated Earnings in Excess of Billings |  |  |
Financing Receivable, Impaired [Line Items] |  |  |
Unapproved change orders | $ 5,000,000 | 2,200,000 |
Claims | 5,000,000 | 9,200,000 |
Unpaid project contract price | 0 | 3,900,000 |
Operating Income (Loss) |  |  |
Financing Receivable, Impaired [Line Items] |  |  |
Estimated construction gross profit (loss), before tax | $ 900,000 | (6,300,000) | $ (9,700,000)
Minimum |  |  |
Financing Receivable, Impaired [Line Items] |  |  |
Revenue recognition, percentage of completion range | 12 months |  |
Warranty term | 1 year |  |
Minimum | Notes Payable for Transportation and Construction Equipment |  |  |
Financing Receivable, Impaired [Line Items] |  |  |
Debt instrument, term | 2 years |  |
Stated interest rate | 3.15% |  |
Maximum |  |  |
Financing Receivable, Impaired [Line Items] |  |  |
Revenue recognition, percentage of completion range | 36 months |  |
Warranty term | 2 years |  |
Maximum | Notes Payable for Transportation and Construction Equipment |  |  |
Financing Receivable, Impaired [Line Items] |  |  |
Debt instrument, term | 5 years |  |
Stated interest rate | 6.92% |  |
JBC Former Owners |  |  |
Financing Receivable, Impaired [Line Items] |  |  |
Business acquisition earn-out expense |  | 1,200,000 |
JBC Former Owners | Other Operating Income (Expense) |  |  |
Financing Receivable, Impaired [Line Items] |  |  |
Business acquisition earn-out expense | $ 1,300,000 |  |
Tealstone |  |  |
Financing Receivable, Impaired [Line Items] |  |  |
Business acquisition earn-out expense | $ 400,000 |  |
Residential Construction |  |  |
Financing Receivable, Impaired [Line Items] |  |  |
Revenue recognition, percentage of completion range | 1 month |  |
Notes Payable for Transportation and Construction Equipment |  |  |
Financing Receivable, Impaired [Line Items] |  |  |
Notes payable for transportation and construction equipment and other | $ 1,557,000 | $ 2,665,000 |
Notes Payable for Transportation and Construction Equipment | Minimum |  |  |
Financing Receivable, Impaired [Line Items] |  |  |
Debt instrument, term | 3 years |  |
Stated interest rate | 3.15% |  |
Notes Payable for Transportation and Construction Equipment | Maximum |  |  |
Financing Receivable, Impaired [Line Items] |  |  |
Debt instrument, term | 5 years |  |
Stated interest rate | 6.92% |  |

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