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Restructuring and Other Charges - Summary of Restructuring and Other Charges Impacts on Reportable Segment Income by Line of Business (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jul. 01, 2022	Jul. 02, 2021	Jul. 01, 2022	Jul. 02, 2021
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges			$ 19,604
Impairment of long-lived assets and equity method investment			74,585	$ 40,138
AWE Management Ltd
Restructuring Cost and Reserve [Line Items]
Gain on termination of lease			(7,100)
Impairment of long-lived assets and equity method investment		$ 38,900		38,900
People & Places Solutions
Restructuring Cost and Reserve [Line Items]
Real estate impairment and other transformation activities			71,200
CH2M HILL Companies, Ltd.
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	$ 4,577	13,768	182,100	92,509
Loss related to settlement			91,300
Real estate impairment and other transformation activities			77,000
CH2M HILL Companies, Ltd. \| Operating profit (mainly SG&A)
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	4,707	8,058	192,782	53,638
CH2M HILL Companies, Ltd. \| Other (Income) Expense, net
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	(130)	5,710	(10,682)	38,871
CH2M HILL Companies, Ltd. \| Corporate
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	4,048	10,904	113,399	65,929
CH2M HILL Companies, Ltd. \| Critical Mission Solutions \| Operating Segments
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	(255)	921	4,361	4,840
CH2M HILL Companies, Ltd. \| People & Places Solutions \| Operating Segments
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	25	592	61,865	7,291
CH2M HILL Companies, Ltd. \| PA Consulting \| Operating Segments
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	$ 759	$ 1,351	$ 2,475	$ 14,449