Employee Benefit Plans - Contributions (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Post Retirement Benefit Plan, Future Employer Contribution in Next Fixcal Year		$ 71
Post employment benefit plan contributions by employer		96	63	66
Defined Benefit Pension Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined benefit pension plan contributions by employer		230
Defined Benefit Plans, Future Employer Contributions in Next Fiscal Year		250
2014		721
2015		639
2016		623
2017		614
2018		579
Years 2019-2022		2,960
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined benefit pension plan contributions by employer		77
2014		71
2015		73
2016		71
2017		70
2018		69
Years 2019-2022		317
Discount rate assumptions used to determine benefit obligations		4.50%	3.60%	4.50%
Discount rate assumptions used to determine net periodic benefit costs	4.50%	3.60%	4.50%	4.90%
Health care cost trend rate assumed for next year		0.072	0.075
Rate to which the cost trend rate is assumed to decline (the ultimate trend rate)		0.049	0.049
Year that the rate reaches the ultimate trend rate		2023	2017
Effect of 1% increase/decrease on total service and interest cost components		1,000,000	(1,000,000)
Effect of 1% increase/decrease on post-retirement benefit obligation		32,000,000	(29,000,000)
United States Pension Plans of US Entity, Defined Benefit [Member] | Defined Benefit Pension Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined benefit pension plan contributions by employer		27
2014		463
2015		374
2016		352
2017		333
2018		290
Years 2019-2022		1,357
Discount rate assumptions used to determine benefit obligations		4.80%	3.70%	4.80%
Rate of compensation increase assumptions used to determine benefit obligation		0.20%	0.20%	3.50%
Discount rate assumptions used to determine net periodic benefit costs	4.80%	3.70%	4.80%	5.10%
Expected return on plan assets assumptions used to determine net periodic benefit cost	7.80%	7.80%	7.80%	8.30%
Rate of compensation increase assumptions used to determine net periodic benefit cost	0.20%	0.20%	3.50%	3.50%
Foreign Pension Plans, Defined Benefit [Member] | Defined Benefit Pension Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined benefit pension plan contributions by employer		203
2014		258
2015		265
2016		271
2017		281
2018		289
Years 2019-2022		1,603
Discount rate assumptions used to determine benefit obligations		4.20%	4.00%	4.60%
Rate of compensation increase assumptions used to determine benefit obligation		2.70%	2.60%	2.70%
Discount rate assumptions used to determine net periodic benefit costs	4.20%	4.00%	4.60%	5.30%
Expected return on plan assets assumptions used to determine net periodic benefit cost	6.10%	6.10%	6.20%	6.60%
Rate of compensation increase assumptions used to determine net periodic benefit cost	2.70%	2.60%	2.70%	2.70%
Foreign Pension Plans, Defined Benefit [Member] | Defined Benefit Pension Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plans, Future Employer Contributions in Next Fiscal Year		160
United States Pension Plans of US Entity, Defined Benefit [Member] | Defined Benefit Pension Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plans, Future Employer Contributions in Next Fiscal Year		$ 90