Employee Benefit Plans (Details) $ in Millions		3 Months Ended		9 Months Ended
	Apr. 03, 2020 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined benefit plan, number of plan participants	3,400
Defined benefit plan, benefit obligation, increase due to remeasurement	$ 2,400
Contributions - Defined benefit plans		$ 22	$ 4	$ 64	$ 41
Contributions - Defined contribution plans		228	117	668	369
Liability, Defined Benefit Pension Plan, Noncurrent		14,688		14,688		$ 2,487
Non-service pension (income) expense		(253)	(289)	(658)	(681)
Total net periodic benefit (income) cost				(325)	(471)
Fair Value, Recurring [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Marketable securities held in trusts		847		847		0
Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Liability, Defined Benefit Pension Plan, Noncurrent		13,499		13,499		1,770
Service cost		149	62	328	208
Interest cost		465	300	1,170	942
Expected return on plan assets		(827)	(551)	(2,162)	(1,687)
Amortization of prior service cost (credit)		13	4	39	13
Recognized actuarial net loss (gain)		86	60	255	158
Net settlement and curtailment loss (gain)		8	(96)	35	(88)
Non-service pension (income) expense		(255)	(283)	(663)	(662)
Total net periodic benefit (income) cost		(106)	(221)	(335)	(454)
Pension Plan [Member] | UNITED STATES
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Contributions - Defined contribution plans		24		101
Other Postretirement Benefits Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Liability, Defined Benefit Pension Plan, Noncurrent		1,059		1,059		696
Service cost		2	0	5	2
Interest cost		10	7	26	23
Expected return on plan assets		(4)	0	(9)	(1)
Amortization of prior service cost (credit)		(1)	(10)	(3)	(32)
Recognized actuarial net loss (gain)		(3)	(3)	(9)	(9)
Net settlement and curtailment loss (gain)		0	0	0	0
Non-service pension (income) expense		2	(6)	5	(19)
Total net periodic benefit (income) cost		4	(6)	10	$ (17)
Other pension and PRB related items
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Liability, Defined Benefit Pension Plan, Noncurrent		$ 130		$ 130		$ 21
UNITED STATES | Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net settlement and curtailment loss (gain)			(98)
Total net periodic benefit (income) cost			10
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)			(425)
Benefit obligation gain [Member] | UNITED STATES | Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)			180
Remeasurement loss [Member] | UNITED STATES | Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)			$ (605)