Pension and Other Postretirement Employee Benefit Plans - Net Periodic Benefit Costs (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Defined Benefit Pension Plans, U.S.
Components of net periodic benefit cost [Abstract]
Benefits earned during the period	$ 78	$ 68
Interest cost on benefit obligations	112	106
Expected return on plan assets	(239)	(195)
Amortization:
Net (gain)/loss	68	72
Prior service cost (credit)	(10)	(11)
Net periodic defined benefit cost	9	40
Other defined benefit pension plans	3	4
Total defined benefit plans	12	44
Total defined contribution plans	105	81
Total pension and OPEB cost included in compensation expense	117	125
Defined Benefit Pension Plans, Non-U.S.
Components of net periodic benefit cost [Abstract]
Benefits earned during the period	9	10
Interest cost on benefit obligations	30	31
Expected return on plan assets	(34)	(33)
Amortization:
Net (gain)/loss	12	9
Prior service cost (credit)	(1)	0
Net periodic defined benefit cost	16	17
Other defined benefit pension plans	2	2
Total defined benefit plans	18	19
Total defined contribution plans	79	80
Total pension and OPEB cost included in compensation expense	97	99
OPEB Plans
Components of net periodic benefit cost [Abstract]
Benefits earned during the period	0	0
Interest cost on benefit obligations	9	11
Expected return on plan assets	(22)	(22)
Amortization:
Net (gain)/loss	1	2
Prior service cost (credit)	0	0
Net periodic defined benefit cost	(12)	(9)
Total defined benefit plans	(12)	(9)
Total pension and OPEB cost included in compensation expense	$ (12)	$ (9)