Employee Benefit Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
U.S. [Member]
Change in Benefit Obligation
Benefit obligation at January 1	$ 14,250	$ 12,080
Service cost	538	450	$ 495
Interest cost	502	494	471
Plan participants' contributions	0	0
Plan amendments	0	0
Actuarial (gain) loss	(345)	2,299
Foreign currency exchange rate changes	0	0
Benefits paid	(1,382)	(1,073)
Divestitures	0	0
Curtailment	0	0
Benefit obligation at December 31	13,563	14,250	12,080
Change in Plan Assets
Fair value of plan assets at January 1	11,090	11,210
Actual return on plan assets	(75)	854
Foreign currency exchange rate changes	0	0
Employer contributions	641	99
Plan participants' contributions	0	0
Benefits paid	(1,382)	(1,073)
Divestitures	0	0
Fair value of plan assets at December 31	10,274	11,090	11,210
Funded Status at December 31	(3,289)	(3,160)
International [Member]
Change in Benefit Obligation
Benefit obligation at January 1	5,767	6,095
Service cost	185	190	197
Interest cost	277	340	314
Plan participants' contributions	6	8
Plan amendments	(6)	3
Actuarial (gain) loss	(309)	336
Foreign currency exchange rate changes	(326)	(348)
Benefits paid	(241)	(293)
Divestitures	0	(564)
Curtailment	(17)	0
Benefit obligation at December 31	5,336	5,767	6,095
Change in Plan Assets
Fair value of plan assets at January 1	4,244	4,543
Actual return on plan assets	112	571
Foreign currency exchange rate changes	(239)	(279)
Employer contributions	227	276
Plan participants' contributions	6	8
Benefits paid	(241)	(293)
Divestitures	0	(582)
Fair value of plan assets at December 31	4,109	4,244	4,543
Funded Status at December 31	(1,227)	(1,523)
Other Benefits [Member]
Change in Benefit Obligation
Benefit obligation at January 1	3,660	3,138
Service cost	72	50	66
Interest cost	151	148	149
Plan participants' contributions	148	150
Plan amendments	0	2
Actuarial (gain) loss	(326)	544
Foreign currency exchange rate changes	(37)	(22)
Benefits paid	(344)	(350)
Divestitures	0	0
Curtailment	0	0
Benefit obligation at December 31	3,324	3,660	3,138
Change in Plan Assets
Fair value of plan assets at January 1	0	0
Actual return on plan assets	0	0
Foreign currency exchange rate changes	0	0
Employer contributions	196	200
Plan participants' contributions	148	150
Benefits paid	(344)	(350)
Divestitures	0	0
Fair value of plan assets at December 31	0	0	$ 0
Funded Status at December 31	$ (3,324)	$ (3,660)