Benefit Plans (Net Funded Status) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
U.S. Defined Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Settlements, Plan Assets	$ (3)	$ 0
CHANGE IN PROJECTED BENEFIT OBLIGATION:
Benefit obligation, beginning period	1,235	1,059
Service cost	16	14	$ 16
Interest cost	48	50	46
Employee contributions	0	0
Plan amendments	5	8
Benefits paid	(61)	(59)
Actuarial (gain) loss	(68)	163
Effect of foreign currency exchange rate changes	0	0
Benefit obligation, ending period	1,172	1,235	1,059
CHANGE IN PLAN ASSETS:
Fair value of plan assets, beginning period	1,061	941
Actual return on plan assets	(7)	123
Employer contributions	31	56
Employee contributions	0	0
Benefits paid	(61)	(59)
Effect of foreign currency exchange rate changes	0	0
Fair value of plan assets, ending period	1,021	1,061	941
Funded status as of December 31	(151)	(174)
Defined Benefit Plan, Settlements, Benefit Obligation	(3)	0
Foreign Defined Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Settlements, Plan Assets	0	0
CHANGE IN PROJECTED BENEFIT OBLIGATION:
Benefit obligation, beginning period	4,363	4,749
Service cost	15	16	26
Interest cost	351	489	515
Employee contributions	3	4
Plan amendments	2	(3)
Benefits paid	(300)	(415)
Actuarial (gain) loss	(160)	87
Effect of foreign currency exchange rate changes	(1,301)	(564)
Benefit obligation, ending period	2,973	4,363	4,749
CHANGE IN PLAN ASSETS:
Fair value of plan assets, beginning period	3,272	3,605
Actual return on plan assets	182	360
Employer contributions	89	135
Employee contributions	3	4
Benefits paid	(300)	(415)
Effect of foreign currency exchange rate changes	(962)	(417)
Fair value of plan assets, ending period	2,284	3,272	$ 3,605
Funded status as of December 31	(689)	(1,091)
Defined Benefit Plan, Settlements, Benefit Obligation	$ 0	$ 0