Pension Plans and Other Post Employment Benefit Plans Amounts Recognized in Consolidated Balance Sheets (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Accumulated Benefit Obligation	$ 21,600	$ 21,000
Noncurrent liabilities	(5,176)	(6,377)
Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net amount recognized	(3,847)	(4,063)
Net loss (gain)	1,886	1,641
Prior service (benefit) cost	(14)	(10)
Pretax balance in accumulated other comprehensive (income) loss at end of year	1,872	1,631
Other Post Employment Benefits Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net amount recognized	(1,571)	(2,591)
Net loss (gain)	163	108
Prior service (benefit) cost	(939)	0
Pretax balance in accumulated other comprehensive (income) loss at end of year	(776)	108
Other Assets [Member] | Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Other Assets	7	10
Other Assets [Member] | Other Post Employment Benefits Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Other Assets	0	0
Accrued and Other Current Liabilities [Member] | Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Current liabilities	(32)	(50)
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	(217)	(237)
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	(3,822)	(4,023)
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	$ (1,354)	$ (2,354)