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Secured Credit Facility and Other Debt - Narrative (Details) |  |  |  | 3 Months Ended | 9 Months Ended |
--- | --- | --- | --- | --- | --- | ---
Apr. 03, 2020 USD ($) | Apr. 03, 2019 USD ($) | Apr. 03, 2017 USD ($) | Sep. 30, 2018 USD ($) | Sep. 30, 2017 USD ($) | Sep. 30, 2018 USD ($) | Sep. 30, 2017 USD ($) | Dec. 31, 2017 USD ($)
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Amortization of debt issuance costs |  |  |  | $ 500,000 | $ 500,000 | $ 1,600,000 | $ 1,000,000 |
Notes and deferred payments to sellers |  |  |  |  |  | 0 | 11,588,000 |
Notes payable for transportation and construction equipment and other |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Notes payable, noncurrent |  |  |  | $ 900,000 |  | $ 900,000 |  | $ 1,600,000
Notes payable for transportation and construction equipment and other | Minimum |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Debt instrument, term |  |  |  |  |  | 3 years |  |
Debt instrument, interest rate, stated percentage |  |  |  | 3.15% |  | 3.15% |  |
Notes payable for transportation and construction equipment and other | Maximum |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Debt instrument, term |  |  |  |  |  | 5 years |  |
Debt instrument, interest rate, stated percentage |  |  |  | 6.92% |  | 6.92% |  |
Warrants to the Lenders Under the Loan Agreement |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Warrants and rights outstanding |  |  | $ 3,500,000 |  |  |  |  |
Notes and deferred payments to sellers, Tealstone acquisition |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Promissory notes issued to the sellers |  |  | 5,000,000 |  |  | $ 5,000,000 |  |
Cash payments to the seller |  |  | 55,000,000 |  |  |  |  |
Notes and deferred payments to sellers |  |  | 11,600,000 |  |  |  |  |
Accretion expense |  |  |  | $ 300,000 | $ 300,000 | $ 900,000 | $ 500,000 |
Notes and deferred payments to sellers, Tealstone acquisition | Scenario, Forecast |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Cash payments to the seller | $ 7,500,000 | $ 2,426,000 |  |  |  |  |  |
Term loan | Senior secured term loans | Loan and security agreement |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Debt instrument face amount |  |  | $ 85,000,000 |  |  |  |  |
Loan prepayment offer required to make quarterly, percentage |  |  | 75.00% |  |  |  |  |
Debt instrument, financial covenants, maximum ratio of secured indebtedness to EBITDA, period one |  |  | 2 |  |  |  |  |
Debt Instrument, financial covenants, maximum ratio of secured indebtedness to EBITDA, period two |  |  | 1.8 |  |  |  |  |
Debt Instrument, financial covenants, minimum daily cash collateral, period two |  |  | $ 15,000,000 |  |  |  |  |
Debt instrument, financial covenants, minimum rolling four quarter gross margin in contract backlog, period one |  |  | 65,000,000 |  |  |  |  |
Debt Instrument, financial covenants, minimum rolling four quarter gross margin in contract backlog, period two |  |  | 70,000,000 |  |  |  |  |
Debt instrument, financial covenants, maximum incurrence of net capital expenditures during each of four consecutive fiscal quarters |  |  | 15,000,000 |  |  |  |  |
Debt instrument, financial covenants, minimum bonding capacity |  |  | 1,000,000,000 |  |  |  |  |
Debt instrument, financial covenants, minimum EBITDA during each four consecutive fiscal quarters |  |  | 12,000,000 |  |  |  |  |
Debt issuance costs, net |  |  | $ 10,400,000 |  |  |  |  |
Debt instrument, term |  |  | 5 years |  |  |  |  |
Term loan | Senior secured term loans | Loan and security agreement | London Interbank Offered Rate (LIBOR) |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Debt instrument, basis spread on variable rate |  |  | 8.75% |  |  |  |  |
Measurement Input, Discount Rate | Notes and deferred payments to sellers, Tealstone acquisition |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Fair value inputs, discount rate |  |  | 0.12 |  |  |  |  |

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