Restructuring and Other Charges - Summary of Restructuring and Other Activities by Major Type of Costs (Details) - CH2M HILL Companies, Ltd. - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 30, 2018	Mar. 31, 2017	Mar. 30, 2018	Mar. 31, 2017
Restructuring Cost and Reserve [Line Items]
Restructuring costs	$ 69,351	$ 52,266	$ 88,701	$ 84,007
Lease Abandonments
Restructuring Cost and Reserve [Line Items]
Restructuring costs	37,073	27,992	40,436	44,601
Involuntary Terminations
Restructuring Cost and Reserve [Line Items]
Restructuring costs	16,936	18,554	19,120	29,886
Outside Services
Restructuring Cost and Reserve [Line Items]
Restructuring costs	8,170	2,261	16,759	3,552
Other
Restructuring Cost and Reserve [Line Items]
Restructuring costs	$ 7,172	$ 3,459	$ 12,386	$ 5,968