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Debt - Narrative (Details) |  |  | 3 Months Ended | 9 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | --- | --- | --- | ---
Sep. 30, 2020 USD ($) entity | Oct. 02, 2019 USD ($) | Sep. 30, 2020 USD ($) entity | Jun. 30, 2020 USD ($) entity loan | Sep. 30, 2019 USD ($) | Sep. 30, 2020 USD ($) entity | Sep. 30, 2019 USD ($) | Dec. 31, 2024 USD ($) | Dec. 31, 2023 USD ($) | Dec. 31, 2022 USD ($) | Dec. 31, 2021 USD ($) | Dec. 31, 2020 USD ($) | Dec. 31, 2019 USD ($) | Dec. 05, 2019 USD ($)
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Long-term debt | $ 400,429,000 |  | $ 400,429,000 |  |  | $ 400,429,000 |  |  |  |  |  |  | $ 443,035,000 |
Amortization of debt issuance costs |  |  | 727,000 |  | $ 0 | 2,219,000 | $ 1,555,000 |  |  |  |  |  |  |
Repayments of debt |  |  |  |  |  | 52,695,000 | $ 10,435,000 |  |  |  |  |  |  |
Finance lease liabilities | $ 610,000 |  | $ 610,000 |  |  | $ 610,000 |  |  |  |  |  |  | 764,000 |
Number of entities | entity | 2 |  | 2 | 2 |  | 2 |  |  |  |  |  |  |  |
Ownership interest in subsidiaries | 50.00% |  | 50.00% | 50.00% |  | 50.00% |  |  |  |  |  |  |  |
Paycheck protection loans received, CARES Act | loan |  |  |  | 3 |  |  |  |  |  |  |  |  |  |
Paycheck protection program loan amount, CARES Act |  |  |  | $ 9,800,000 |  |  |  |  |  |  |  |  |  |
Plateau Excavation |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Liabilities incurred |  | $ 10,000,000 |  |  |  |  |  |  |  |  |  |  |  |
Tealstone Construction |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Repayment of deferred cash payment |  |  |  |  |  | $ 5,000,000 |  |  |  |  |  |  |  |
Secured Debt |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fixed charge ratio minimum |  |  |  |  |  | 1.20 |  |  |  |  |  |  |  |
Secured Debt | Credit Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument face amount |  | 475,000,000 |  |  |  |  |  |  |  |  |  |  |  |
Secured Debt | Credit Facility |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Long-term debt | $ 380,000,000 |  | $ 380,000,000 |  |  | $ 380,000,000 |  |  |  |  |  |  | 420,000,000 |
Secured Debt | Term Loan Facility |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Long-term debt | $ 380,000,000 |  | $ 380,000,000 |  |  | $ 380,000,000 |  |  |  |  |  |  | 400,000,000 |
Weighted average interest rate | 5.80% |  | 5.80% |  |  | 5.80% |  |  |  |  |  |  |  |
Notes Payable, Other Payables | Plateau Excavation |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Liabilities incurred |  | $ 10,000,000 |  |  |  |  |  |  |  |  |  |  |  |
Stated interest rate |  | 8.00% |  |  |  |  |  |  |  |  |  |  |  |
Notes Payable, Other Payables | Tealstone Construction |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Long-term debt | $ 0 |  | $ 0 |  |  | $ 0 |  |  |  |  |  |  | $ 12,230,000 |
Repayments of debt |  |  |  |  |  | $ 7,500,000 |  |  |  |  |  |  |  |
Notes Payable, Other Payables | Notes payable for transportation and construction equipment and other | Minimum |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stated interest rate | 2.99% |  | 2.99% |  |  | 2.99% |  |  |  |  |  |  |  |
Debt instrument, term |  |  |  |  |  | 3 years |  |  |  |  |  |  |  |
Notes Payable, Other Payables | Notes payable for transportation and construction equipment and other | Maximum |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stated interest rate | 6.92% |  | 6.92% |  |  | 6.92% |  |  |  |  |  |  |  |
Debt instrument, term |  |  |  |  |  | 5 years |  |  |  |  |  |  |  |
Revolving Credit Facility | Secured Debt | Term Loan Facility |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument face amount |  | $ 400,000,000 |  |  |  |  |  |  |  |  |  |  |  |
Revolving Credit Facility | Line of Credit | Revolving Credit Facility |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Line of credit, maximum borrowing capacity |  | 75,000,000 |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, base interest rate | 4.25% |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, LIBOR interest rate | 0.162% |  |  |  |  |  |  |  |  |  |  |  |  |
Line of credit, remaining borrowing capacity | $ 75,000,000 |  | $ 75,000,000 |  |  | $ 75,000,000 |  |  |  |  |  |  |  |
Weighted average interest rate | 6.68% |  | 6.68% |  |  | 6.68% |  |  |  |  |  |  |  |
Revolving Credit Facility | Line of Credit | Revolving Credit Facility | Base Rate |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Basis spread on variable rate | 3.50% |  |  |  |  |  |  |  |  |  |  |  |  |
Revolving Credit Facility | Line of Credit | Revolving Credit Facility | London Interbank Offered Rate (LIBOR) |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Basis spread on variable rate | 4.50% |  |  |  |  |  |  |  |  |  |  |  |  |
Swing Line Loan | Line of Credit | Revolving Credit Facility |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Line of credit, maximum borrowing capacity |  | $ 15,000,000 |  |  |  |  |  |  |  |  |  |  |  |
Interest Rate Swap | Secured Debt |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative, notional amount | $ 350,000,000 |  | $ 350,000,000 |  |  | $ 350,000,000 |  |  |  |  |  |  |  | $ 350,000,000
Forecast | Secured Debt | Term Loan Facility |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Periodic payments |  |  |  |  |  |  |  | $ 220,000,000 | $ 50,000,000 | $ 50,000,000 | $ 50,000,000 | $ 30,000,000 |  |
October 1, 2019 - June 30, 2020 | Secured Debt | Credit Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Leverage ratio maximum |  |  |  |  |  | 4.00 |  |  |  |  |  |  |  |
July 1, 2020 - September 30, 2020 | Secured Debt | Credit Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Leverage ratio maximum |  |  |  |  |  | 3.75 |  |  |  |  |  |  |  |
October 1, 2020 - March 31, 2021 | Secured Debt | Credit Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Leverage ratio maximum |  |  |  |  |  | 3.50 |  |  |  |  |  |  |  |
April 1, 2021 - June 30, 2021 | Secured Debt | Credit Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Leverage ratio maximum |  |  |  |  |  | 3.25 |  |  |  |  |  |  |  |
October 1, 2021 - December 31, 2021 | Secured Debt | Credit Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Leverage ratio maximum |  |  |  |  |  | 3.00 |  |  |  |  |  |  |  |

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