Description of Business	12 Months Ended
	Oct. 03, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business	Description of BusinessWe are a leading global provider of consulting and engineering services that focuses on water, environment, sustainable infrastructure, renewable energy, and international development. We are a global company that is Leading with Science® to provide innovative solutions for our public and private clients. We typically begin at the earliest stage of a project by identifying technical solutions and developing execution plans tailored to our clients’ needs and resources. Our solutions may span the entire life cycle of consulting and engineering projects and include applied science, data analysis, research, engineering, design, project management, and operations and maintenance.We manage our business under two reportable segments. Our Government Services Group (“GSG”) reportable segment primarily includes activities with U.S. government clients (federal, state and local) and all activities with development agencies worldwide. Our Commercial/International Services Group (“CIG”) reportable segment primarily includes activities with U.S. commercial clients and international clients other than development agencies. We continue to report the historical results of the wind-down of our non-core construction activities in the Remediation and Construction Management (“RCM”) reportable segment.