Employee Benefit Plans - Net Periodic Benefit Cost (Credit) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Domestic Pension Benefits
Components of net periodic benefit cost (credit):
Service cost	$ 15	$ 14
Interest cost	43	45
Expected return on assets	(83)	(79)
Curtailment (gain)/loss	(30)	0
Other	31	28
Net periodic benefit cost (credit)	(24)	8
Foreign Pension Benefits
Components of net periodic benefit cost (credit):
Service cost	8	9
Interest cost	10	11
Expected return on assets	(13)	(15)
Curtailment (gain)/loss	0	0
Other	6	4
Net periodic benefit cost (credit)	11	9
Health care benefits
Components of net periodic benefit cost (credit):
Service cost	1	1
Interest cost	2	3
Expected return on assets	(2)	(2)
Curtailment (gain)/loss	0	0
Other	0	0
Net periodic benefit cost (credit)	$ 1	$ 2