Postretirement Benefit Plans - Expenses Related to Defined Benefit and Retiree Health Care benefit Plans (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
U.S. defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 5	$ 5	$ 11	$ 10
Interest cost	11	11	21	22
Expected return on plan assets	(12)	(11)	(24)	(21)
Recognized net actuarial loss	5	7	10	13
Amortization of prior service cost (credit)	0	0	0	0
Net periodic benefit costs	9	12	18	24
Settlement losses	11	2	12	3
Total, including other postretirement losses	20	14	30	27
U.S. retiree health care plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	2	1	3	2
Interest cost	5	6	10	11
Expected return on plan assets	(6)	(5)	(11)	(10)
Recognized net actuarial loss	2	2	4	4
Amortization of prior service cost (credit)	2	1	3	2
Net periodic benefit costs	5	5	9	9
Settlement losses	0	0	0	0
Total, including other postretirement losses	5	5	9	9
Non-U.S. defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	8	10	17	20
Interest cost	14	18	27	35
Expected return on plan assets	(19)	(22)	(38)	(41)
Recognized net actuarial loss	6	7	12	13
Amortization of prior service cost (credit)	(1)	0	(1)	(1)
Net periodic benefit costs	8	13	17	26
Settlement losses	2	0	2	0
Total, including other postretirement losses	$ 10	$ 13	$ 19	$ 26