Restructuring and Other Charges - Narrative (Details) $ in Millions	3 Months Ended				6 Months Ended
	Mar. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Mar. 27, 2015 Business	Mar. 30, 2018 USD ($)
Restructuring Cost and Reserve [Line Items]
Restructuring pre-tax net charges			$ 22.6
Net realizable value write-offs on contract accounts receivables			16.5
Statutory redundancy and severance costs			1.4
Other liabilities			$ 4.7
Additional charges recorded under business exit		$ 1.2
Number of lines of business | Business				4
CH2M HILL Companies, Ltd.
Restructuring Cost and Reserve [Line Items]
Restructuring pre-tax net charges	$ 55.2				$ 60.7
Integration related costs	$ 14.2				$ 28.0