Pensions and Other Postretirement Benefits (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 28, 2015	Jun. 29, 2014	Jun. 28, 2015	Jun. 29, 2014	Dec. 28, 2014
General Discussion of Pension and Other Postretirement Benefits [Abstract]
Net pension and post-retirement benefit (losses)/gains	$ (18)	$ (28)	$ (19)	$ (28)
Benefit obligation recognized for pension benefits as other non-current assets	617		617		$ 581
Employer contribution			33
Expected full year combined cash contributions			60
Pension Benefits
Components of net periodic benefit cost
Service cost	7	8	13	15
Interest cost	26	35	52	70
Expected return on plan assets	(45)	(55)	(93)	(111)
Amortization of prior service cost/(credit)	0	0	0	0
Amortization of unrecognized gains/(losses)	1	0	2	0
Settlements	9	0	9	0
Net periodic benefit (income)/expense	(2)	(12)	(17)	(26)
General Discussion of Pension and Other Postretirement Benefits [Abstract]
Defined benefit plan, settlement loss	9	0	9	0
Other Retiree Benefits
Components of net periodic benefit cost
Service cost	1	1	2	2
Interest cost	2	2	4	4
Expected return on plan assets	0	0	0	0
Amortization of prior service cost/(credit)	(2)	(2)	(3)	(3)
Amortization of unrecognized gains/(losses)	0	0	0	0
Settlements	0	0	0	0
Net periodic benefit (income)/expense	1	1	3	3
General Discussion of Pension and Other Postretirement Benefits [Abstract]
Defined benefit plan, settlement loss	0	$ 0	0	$ 0
UNITED KINGDOM
General Discussion of Pension and Other Postretirement Benefits [Abstract]
Defined benefit plan, curtailment gain	2
Net pension and post-retirement benefit (losses)/gains	(15)
CANADA
Components of net periodic benefit cost
Settlements			11
General Discussion of Pension and Other Postretirement Benefits [Abstract]
Net pension and post-retirement benefit (losses)/gains	$ (4)
Defined benefit plan, settlement loss			$ 11