Pension and Other Postretirement Employee Benefit Plans - Net Periodic Benefit Costs (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Defined Benefit Pension Plans, U.S.
Components of net periodic benefit cost [Abstract]
Benefits earned during the period	$ 79	$ 68	$ 157	$ 136
Interest cost on benefit obligations	111	121	223	227
Expected return on plan assets	(238)	(223)	(477)	(418)
Amortization:
Net (gain)/loss	67	73	135	145
Prior service cost (credit)	(11)	(10)	(21)	(21)
Net periodic defined benefit cost	8	29	17	69
Other defined benefit pension plans	4	3	7	7
Total defined benefit plans	12	32	24	76
Total defined contribution plans	115	107	220	188
Total pension and OPEB cost included in compensation expense	127	139	244	264
Defined Benefit Pension Plans, Non-U.S.
Components of net periodic benefit cost [Abstract]
Benefits earned during the period	8	9	17	19
Interest cost on benefit obligations	30	31	60	62
Expected return on plan assets	(34)	(34)	(68)	(67)
Amortization:
Net (gain)/loss	12	8	24	17
Prior service cost (credit)	0	0	(1)	0
Net periodic defined benefit cost	16	14	32	31
Other defined benefit pension plans	4	1	6	3
Total defined benefit plans	20	15	38	34
Total defined contribution plans	80	75	159	155
Total pension and OPEB cost included in compensation expense	100	90	197	189
OPEB Plans
Components of net periodic benefit cost [Abstract]
Benefits earned during the period	0	0	0	0
Interest cost on benefit obligations	9	11	18	22
Expected return on plan assets	(24)	(23)	(46)	(45)
Amortization:
Net (gain)/loss	0	(2)	1	0
Prior service cost (credit)	0	0	0	0
Net periodic defined benefit cost	(15)	(14)	(27)	(23)
Total defined benefit plans	(15)	(14)	(27)	(23)
Total pension and OPEB cost included in compensation expense	$ (15)	$ (14)	$ (27)	$ (23)