Description of Business and Basis of Presentation	12 Months Ended
Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business and Basis of Presentation	Orion Group Holdings, Inc. and Subsidiaries Notes to Consolidated Financial Statements Years Ended December 31, 2020, 2019 and 2018 (Tabular Amounts in thousands, Except Share and per Share Amounts) 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 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 These consolidated financial statements include the accounts of the parent company, Orion Group Holdings, Inc. and its wholly-owned subsidiaries and have been prepared in accordance with U.S. GAAP. All intercompany balances and transactions have been eliminated in consolidation.

Description of Business and Basis of Presentation

12 Months Ended

Dec. 31, 2020

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Description of Business and Basis of Presentation

Orion Group Holdings, Inc. and Subsidiaries

Notes to Consolidated Financial Statements

Years Ended December 31, 2020, 2019 and 2018

(Tabular Amounts in thousands, Except Share and per Share Amounts)

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 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

These consolidated financial statements include the accounts of the parent company, Orion Group Holdings, Inc. and its wholly-owned subsidiaries and have been prepared in accordance with U.S. GAAP. All intercompany balances and transactions have been eliminated in consolidation.