Employee Benefit Plans - Components of Net Periodic Benefit Cost (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
United States Pension Plans of US Entity, Defined Benefit [Member]
Net periodic benefit cost of all defined benefit plans
Service cost	$ 138	$ 170	$ 225
Interest cost	143	186	247
Expected return on plan assets	(186)	(223)	(280)
Amortization of prior service cost (credit)	6	7	9
Recognized net actuarial loss (gain)	151	191	165
Settlements	67	181	21
Net periodic benefit cost	319	512	387
Foreign Pension Plans, Defined Benefit [Member]
Net periodic benefit cost of all defined benefit plans
Service cost	102	91	98
Interest cost	145	152	178
Expected return on plan assets	(160)	(158)	(175)
Amortization of prior service cost (credit)	(7)	(8)
Recognized net actuarial loss (gain)	73	59	46
Net periodic benefit cost	153	136	147
Other Postretirement Benefit Plans, Defined Benefit [Member]
Net periodic benefit cost of all defined benefit plans
Service cost	3	6	10
Interest cost	26	33	42
Amortization of prior service cost (credit)	(4)	(4)	(7)
Recognized net actuarial loss (gain)	3		(5)
Net periodic benefit cost	$ 28	$ 35	$ 40