Employee Benefit Plans	9 Months Ended
Sep. 30, 2021
Compensation And Retirement Disclosure [Abstract]
Employee Benefit Plans	Note 12. Employee Benefit Plans Certain Company subsidiaries, including certain subsidiaries in Canada, contribute amounts to multiemployer pension plans and other multiemployer benefit plans and trusts, which are recorded as a component of employee wages and salaries within costs of revenue. Contributions are generally based on fixed amounts per hour per employee for employees covered under these plans. Multiemployer plan contribution rates are determined annually and assessed on a pay-as-you-go basis based on union employee payrolls. Union payrolls cannot be determined for future periods because the number of union employees employed at a given time, and the plans in which they participate, vary depending upon the location and number of ongoing projects and the need for union resources in connection with those projects. Total consolidated contributions to multiemployer plans were $26 and $25 during the three months ended September 30, 2021 and 2020, respectively and $69 and $71 during the nine months ended September 30, 2021 and 2020, respectively. The Company also has a trustee-administered profit sharing retirement plan covering substantially all of the Company's employees in the U.S. not covered by collective bargaining agreements and also adopted a profit sharing plan for employees in Canada (collectively, “Profit Sharing Plans”). The Profit Sharing Plans provide for annual discretionary contributions in amounts based on a performance grid as determined by the Company’s directors. In connection with these plans, the Company recognized $4 and less than $1 in expense during the three months ended September 30, 2021 and 2020, respectively and $11 and $6 in expense during the nine months ended September 30, 2021 and 2020, respectively. Effective January 1, 2021, most of the Company’s employees in the U.S and Canada, including named executive officers, are eligible to participate in the Company’s Employee Stock Purchase Plan (the “ESPP”). Sales of shares of the Company’s common stock under the ESPP are generally made pursuant to offerings that are intended to satisfy the requirements of Section 423 of the Internal Revenue Code. The ESPP permits employees of the Company to purchase common stock at a price equal to 85% of the lesser of (i) the market value of the common stock on the first day of the offering period, or (ii) the market value of the common stock on the purchase date, whichever is lower. Participants are subject to eligibility requirements and may not purchase more than 500 shares in any offering period or more than ten thousand dollars of common stock in a year under the ESPP. During the three and nine months ended September 30, 2021, the Company has recognized $1 and $3 of expense, respectively, and issued 411,320 shares of the Company's common stock related to the ESPP.

Employee Benefit Plans

9 Months Ended

Sep. 30, 2021

Compensation And Retirement Disclosure [Abstract]

Note 12. Employee Benefit Plans

Certain Company subsidiaries, including certain subsidiaries in Canada, contribute amounts to multiemployer pension plans and other multiemployer benefit plans and trusts, which are recorded as a component of employee wages and salaries within costs of revenue. Contributions are generally based on fixed amounts per hour per employee for employees covered under these plans. Multiemployer plan contribution rates are determined annually and assessed on a pay-as-you-go basis based on union employee payrolls. Union payrolls cannot be determined for future periods because the number of union employees employed at a given time, and the plans in which they participate, vary depending upon the location and number of ongoing projects and the need for union resources in connection with those projects. Total consolidated contributions to multiemployer plans were $26 and $25 during the three months ended September 30, 2021 and 2020, respectively and $69 and $71 during the nine months ended September 30, 2021 and 2020, respectively.

The Company also has a trustee-administered profit sharing retirement plan covering substantially all of the Company's employees in the U.S. not covered by collective bargaining agreements and also adopted a profit sharing plan for employees in Canada (collectively, “Profit Sharing Plans”). The Profit Sharing Plans provide for annual discretionary contributions in amounts based on a performance grid as determined by the Company’s directors. In connection with these plans, the Company recognized $4 and less than $1 in expense during the three months ended September 30, 2021 and 2020, respectively and $11 and $6 in expense during the nine months ended September 30, 2021 and 2020, respectively.

Effective January 1, 2021, most of the Company’s employees in the U.S and Canada, including named executive officers, are eligible to participate in the Company’s Employee Stock Purchase Plan (the “ESPP”). Sales of shares of the Company’s common stock under the ESPP are generally made pursuant to offerings that are intended to satisfy the requirements of Section 423 of the Internal Revenue Code. The ESPP permits employees of the Company to purchase common stock at a price equal to 85% of the lesser of (i) the market value of the common stock on the first day of the offering period, or (ii) the market value of the common stock on the purchase date, whichever is lower. Participants are subject to eligibility requirements and may not purchase more than 500 shares in any offering period or more than ten thousand dollars of common stock in a year under the ESPP. During the three and nine months ended September 30, 2021, the Company has recognized $1 and $3 of expense, respectively, and issued 411,320 shares of the Company's common stock related to the ESPP.