Employee Benefit Plans - Net Periodic Benefit Cost (Credit) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Domestic Pension Benefits
Components of net periodic benefit cost (credit):
Service cost	$ 0	$ 15
Interest cost	45	43
Expected return on assets	(82)	(83)
Curtailment (gain)	0	(30)
Other	18	31
Net periodic benefit (credit) cost	(19)	(24)
Foreign Pension Benefits
Components of net periodic benefit cost (credit):
Service cost	8	8
Interest cost	9	10
Expected return on assets	(13)	(13)
Curtailment (gain)	0	0
Other	4	6
Net periodic benefit (credit) cost	8	11
Health care benefits
Components of net periodic benefit cost (credit):
Service cost	1	1
Interest cost	2	2
Expected return on assets	(2)	(2)
Curtailment (gain)	0	0
Other	(1)	0
Net periodic benefit (credit) cost	$ 0	$ 1