Employee Postretirement Benefits (Summarized Financial Information about Postretirement plans, Excluding Defined Contribution Retirement Plans) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Pension Plans
Benefit obligation at beginning of year	$ 3,959	$ 6,860
Service cost	42	38	$ 46
Interest cost	148	187	279
Actuarial loss (gain)	501	(150)
Currency and other	(304)	(139)
Benefit payments from plans	(202)	(235)
Direct benefit payments	(15)	(12)
Settlements	(3)	(2,590)
Benefit obligation at end of year	4,126	3,959	6,860
Fair value of plan assets at beginning of year	3,508	5,914
Actual return on plan assets	413	54
Employer contributions	108	484
Currency and other	(290)	(119)
Benefit payments	(202)	(235)
Settlements	(3)	(2,590)
Fair value of plan assets at end of year	3,534	3,508	5,914
Funded Status	(592)	(451)
Other Postretirement Benefit Plans
Service cost	11	12	13
Interest cost	33	32	35
Settlements	0	0
Other Postretirement Benefit Plans, Defined Benefit
Benefit obligation at beginning of year	717	788
Service cost	11	12
Interest cost	33	32
Actuarial loss (gain)	41	(53)
Currency and other	9	(8)
Benefit payments from plans	0	0
Direct benefit payments	(53)	(54)
Benefit obligation at end of year	758	717	788
Fair value of plan assets at beginning of year	0	0
Actual return on plan assets	0	0
Employer contributions	0	0
Currency and other	0	0
Benefit payments	0	0
Settlements	0	0
Fair value of plan assets at end of year	0	0	$ 0
Funded Status	$ (758)	$ (717)