Pension Plans and Other Post Employment Benefit Plans Amounts Recognized in Consolidated Balance Sheets (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Accumulated Benefit Obligation	$ 23,100	$ 25,100
Noncurrent liabilities	(6,683)	(7,787)
Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Other Assets	11	47
Net amount recognized	(4,496)	(5,266)
Net (gain) loss	737	(165)
Prior service cost	17	0
Pretax balance in accumulated other comprehensive (income) loss at end of year	754	(165)
Other Post Employment Benefits Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Other Assets	0	0
Net amount recognized	(2,514)	(2,810)
Net (gain) loss	(104)	68
Prior service cost	0	0
Pretax balance in accumulated other comprehensive (income) loss at end of year	(104)	68
Accrued and Other Current Liabilities [Member] | Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Current liabilities	(95)	(86)
Accrued and Other Current Liabilities [Member] | Other Post Employment Benefits Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Current liabilities	(243)	(250)
Pension and other post employment benefits - noncurrent [Member] | Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Noncurrent liabilities	(4,412)	(5,227)
Pension and other post employment benefits - noncurrent [Member] | Other Post Employment Benefits Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Noncurrent liabilities	$ (2,271)	$ (2,560)