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
Dec. 30, 2022	Dec. 31, 2021
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	$ 6,685
Real estate impairment charges	27,100	$ 72,300
Gain (loss) on termination of lease	600	6,900
CH2M HILL Companies, Ltd.
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	34,443	69,359
Real estate impairment charges	27,800	71,000
CH2M HILL Companies, Ltd. \| Operating profit (mainly SG&A)
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	35,072	77,903
CH2M HILL Companies, Ltd. \| Other (Income) Expense, net
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	(629)	(8,544)
CH2M HILL Companies, Ltd. \| Corporate
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	3,333	6,838
CH2M HILL Companies, Ltd. \| Critical Mission Solutions \| Operating Segments
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	2,212	1,153
CH2M HILL Companies, Ltd. \| People & Places Solutions \| Operating Segments
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	27,317	61,169
CH2M HILL Companies, Ltd. \| Divergent Solutions \| Operating Segments
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	1,581	0
CH2M HILL Companies, Ltd. \| PA Consulting \| Operating Segments
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	$ 0	$ 199

Amount of gain (loss) on termination of lease before expiration of lease term.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
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The charge against earnings in the period to reduce the carrying amount of real property to fair value.

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Amount of expenses associated with exit or disposal activities pursuant to an authorized plan. Excludes expenses related to a discontinued operation or an asset retirement obligation.

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