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. 31, 2021	Jan. 01, 2021
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	$ (1,594)
Impairment of long-lived assets and equity method investment	72,266	$ 27,902
AWE Management Ltd
Restructuring Cost and Reserve [Line Items]
Impairment of long-lived assets and equity method investment		27,900
Gain on termination of lease	6,900
CH2M HILL Companies, Ltd.
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	69,359	48,393
CH2M HILL Companies, Ltd. \| Continuing Operations \| Other Expense
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	77,900	20,500
CH2M HILL Companies, Ltd. \| Corporate
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	6,838	40,017
CH2M HILL Companies, Ltd. \| Critical Mission Solutions \| Operating Segments
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	1,153	3,209
CH2M HILL Companies, Ltd. \| People & Places Solutions \| Operating Segments
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	61,169	5,167
CH2M HILL Companies, Ltd. \| PA Consulting \| Operating Segments
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	$ 199	$ 0

This item represents an other than temporary decline in value that has been recognized against an investment accounted for under the equity method of accounting. The excess of the carrying amount over the fair value of the investment represents the amount of the write down which is or was reflected in earnings. The written down value is a new cost basis with the adjusted value of the investment becoming its new carrying value subject to the equity accounting method. Evidence of a loss in value might include, but would not necessarily be limited to, absence of an ability to recover the carrying amount of the investment or inability of the investee to sustain an earnings capacity which would justify the carrying amount of the investment.

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

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