Commitments and Contingencies - Environmental remediation (Details) - Environmental liabilities - USD ($) $ in Millions	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Jan. 02, 2016
Environmental Remediation
Environmental reserves	$ 65
Estimated period over which accrued environmental remediation liabilities are likely to be paid	10 years
Accrued environmental remediation liabilities classified as current liabilities	$ 13
Expenditures to evaluate and remediate contaminated sites	18	$ 15	$ 15
Minimum
Environmental Remediation
Potential environmental liabilities	40
Maximum
Environmental Remediation
Potential environmental liabilities	$ 140