Description of Business and Basis of Presentation	6 Months Ended
Jun. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business and Basis of Presentation	1.Description of Business and Basis of Presentation Description of Business Orion Group Holdings, Inc., its subsidiaries and affiliates (hereafter collectively referred to as the "Company"), provide a broad range of specialty construction services in the infrastructure, industrial, and building sectors of the continental United States, Alaska, Canada and the Caribbean Basin. The Company’s marine segment services the infrastructure sector through marine transportation facility construction, marine pipeline construction, marine environmental structures, dredging of waterways, channels and ports, environmental dredging, design, and specialty services. Its concrete segment services the building sector by providing turnkey concrete construction services including pour and finish, dirt work, layout, forming, rebar, and mesh across the light commercial, structural and other associated business areas. The Company is headquartered in Houston, Texas with offices throughout its operating areas. The tools used by the chief operating decision maker ("CODM") to allocate resources and assess performance are based on two reportable and operating segments: marine, which operates under the Orion Marine Group brand and logo, and concrete, which operates under the TAS Commercial Concrete brand and logo. Although we describe the business in this report in terms of the services the Company provides, its base of customers and the areas in which it operates, the Company has determined that its operations currently comprise two reportable segments pursuant to Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) Topic 280, Segment Reporting. In making this determination, the Company considered the similar economic characteristics of its operations that comprise its marine segment. For the marine segment, the methods used, and the internal processes employed, to deliver marine construction services are similar throughout the segment, including standardized estimating, project controls and project management. This segment has the same customers with similar funding drivers, and it complies with regulatory environments driven through Federal agencies such as the U.S. Army Corps of Engineers, U.S. Fish and Wildlife Service, U.S. Environmental Protection Agency and U.S. Occupational Safety and Health Administration ("OSHA"), among others. Additionally, the segment is driven by macro-economic considerations including the level of import/export seaborne transportation, development of energy-related infrastructure, cruise line expansion and operations, marine bridge infrastructure development, waterway pipeline crossings and the maintenance of waterways. These considerations, and others, are key catalysts for future prospects and are similar across the segment. For the concrete segment, the Company also considered the similar economic characteristics of these operations. The methods used, and the internal processes employed, to deliver concrete construction services are similar throughout the segment, including standardized estimating, project controls and project management. This segment complies with regulatory environments such as OSHA. Additionally, this segment is driven by macro-economic considerations, including movements in population, commercial real estate development, institutional funding and expansion, and recreational development, specifically in metropolitan areas of Texas. These considerations, and others, are key catalysts for future prospects and are similar across the segment. Basis of Presentation The accompanying condensed consolidated financial statements and financial information included herein have been prepared pursuant to the interim period reporting requirements of Form 10-Q. Consequently, certain information and note disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States (“U.S. GAAP”) have been condensed or omitted. Readers of this report should also read the Company’s condensed consolidated financial statements and the notes thereto included in its Annual Report on Form 10-K for the fiscal year ended December 31, 2019 (“2019 Form 10-K”) as well as Item 7 – Management’s Discussion and Analysis of Financial Condition and Results of Operations also included in its 2019 Form 10-K. In the opinion of management, the accompanying unaudited condensed consolidated financial statements contain all adjustments considered necessary for a fair presentation of the Company’s financial position, results of operations, and cash flows for the periods presented. Such adjustments are of a normal recurring nature. Interim results of operations for the three and six months ended June 30, 2020 are not necessarily indicative of the results that may be expected for the year ending December 31, 2020. Certain amounts in the prior year financial statements have been reclassified to conform to the current year presentation in the Company’s condensed consolidated statement of operations. As part of the Company’s Invest, Scale and Grow (“ISG”) initiative it realigned its project management personnel within the operating groups for the combined company. As a result of the realignment, beginning in the second quarter of 2019, the Company has elected to classify certain project management costs in Cost of contract revenue in its Condensed Consolidated Statements of Operations (the “Statements of Operations”) to better represent how those costs are managed and controlled. For periods reported prior to the second quarter of 2019, certain project management costs were included in Selling, general and administrative (“SG&A”) expenses. The Company’s SG&A expense for 2019 included project management costs of $1.1 million incurred in the first quarter of 2019.

Description of Business and Basis of Presentation

6 Months Ended

Jun. 30, 2020

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Description of Business and Basis of Presentation

1.Description of Business and Basis of Presentation

Description of Business

Orion Group Holdings, Inc., its subsidiaries and affiliates (hereafter collectively referred to as the "Company"), provide a broad range of specialty construction services in the infrastructure, industrial, and building sectors of the continental United States, Alaska, Canada and the Caribbean Basin. The Company’s marine segment services the infrastructure sector through marine transportation facility construction, marine pipeline construction, marine environmental structures, dredging of waterways, channels and ports, environmental dredging, design, and specialty services. Its concrete segment services the building sector by providing turnkey concrete construction services including pour and finish, dirt work, layout, forming, rebar, and mesh across the light commercial, structural and other associated business areas. The Company is headquartered in Houston, Texas with offices throughout its operating areas.

The tools used by the chief operating decision maker ("CODM") to allocate resources and assess performance are based on two reportable and operating segments: marine, which operates under the Orion Marine Group brand and logo, and concrete, which operates under the TAS Commercial Concrete brand and logo.

Although we describe the business in this report in terms of the services the Company provides, its base of customers and the areas in which it operates, the Company has determined that its operations currently comprise two reportable segments pursuant to Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) Topic 280, Segment Reporting.

In making this determination, the Company considered the similar economic characteristics of its operations that comprise its marine segment. For the marine segment, the methods used, and the internal processes employed, to deliver marine construction services are similar throughout the segment, including standardized estimating, project controls and project management. This segment has the same customers with similar funding drivers, and it complies with regulatory environments driven through Federal agencies such as the U.S. Army Corps of Engineers, U.S. Fish and Wildlife Service, U.S. Environmental Protection Agency and U.S. Occupational Safety and Health Administration ("OSHA"), among others. Additionally, the segment is driven by macro-economic considerations including the level of import/export seaborne transportation, development of energy-related infrastructure, cruise line expansion and operations, marine bridge infrastructure development, waterway pipeline crossings and the maintenance of waterways. These considerations, and others, are key catalysts for future prospects and are similar across the segment.

For the concrete segment, the Company also considered the similar economic characteristics of these operations. The methods used, and the internal processes employed, to deliver concrete construction services are similar throughout the segment, including standardized estimating, project controls and project management. This segment complies with regulatory environments such as OSHA. Additionally, this segment is driven by macro-economic considerations, including movements in population, commercial real estate development, institutional funding and expansion, and recreational development, specifically in metropolitan areas of Texas. These considerations, and others, are key catalysts for future prospects and are similar across the segment.

Basis of Presentation

The accompanying condensed consolidated financial statements and financial information included herein have been prepared pursuant to the interim period reporting requirements of Form 10-Q. Consequently, certain information and note disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States (“U.S. GAAP”) have been condensed or omitted. Readers of this report should also read the Company’s condensed consolidated financial statements and the notes thereto included in its Annual Report on Form 10-K for the fiscal year ended December 31, 2019 (“2019 Form 10-K”) as well as Item 7 – Management’s Discussion and Analysis of Financial Condition and Results of Operations also included in its 2019 Form 10-K.

In the opinion of management, the accompanying unaudited condensed consolidated financial statements contain all adjustments considered necessary for a fair presentation of the Company’s financial position, results of operations, and cash flows for the periods presented. Such adjustments are of a normal recurring nature. Interim results of operations for the three and six months ended June 30, 2020 are not necessarily indicative of the results that may be expected for the year ending December 31, 2020.

Certain amounts in the prior year financial statements have been reclassified to conform to the current year presentation in the Company’s condensed consolidated statement of operations. As part of the Company’s Invest, Scale and Grow (“ISG”) initiative it realigned its project management personnel within the operating groups for the combined company. As a result of the realignment, beginning in the second quarter of 2019, the Company has elected to classify certain project management costs in Cost of contract revenue in its Condensed Consolidated Statements of Operations (the “Statements of Operations”) to better represent how those costs are managed and controlled. For periods reported prior to the second quarter of 2019, certain project management costs were included in Selling, general and administrative (“SG&A”) expenses. The Company’s SG&A expense for 2019 included project management costs of $1.1 million incurred in the first quarter of 2019.