Employee Benefit Plans - Total Recognized in Net Periodic Benefit Cost and Other Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2018
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plans	$ 58	$ 109	$ 175
Net actuarial (gain) loss	117	(275)	273
Amortization of net actuarial (loss) gain	(138)	(156)	(252)
Amortization of net prior service credit	(80)	(81)	(26)
Total Recognized in Other Comprehensive Income	(112)	65	(540)
Interest expense on non-TRA obligations	184	243	258
Interest (income) expense allocated to TRA participant accounts	125	128	(46)
Expected Investment Income on Non-TRA Assets	283	315	357
Actual investment income (loss) on TRA assets	125	128	(46)
Other Postretirement Benefits Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	2	2	4
Interest cost	12	15	23
Expected return on plan assets	0	0	0
Recognized net actuarial loss (gain)	(1)	(5)	0
Amortization of prior service credit	(76)	(77)	(19)
Recognized settlement loss	0	0	0
Recognized curtailment gain	0	0	0
Defined Benefit Plans	(63)	(65)	8
Net Periodic Benefit Cost (Credit)	(63)	(65)	8
Net actuarial (gain) loss	4	8	(63)
Prior service cost (credit)	(11)	0	(234)
Amortization of net actuarial (loss) gain	1	5	0
Amortization of net prior service credit	76	77	19
Curtailment gain	0	0	0
Total Recognized in Other Comprehensive Income	70	90	(278)
Total Recognized in Net Periodic Benefit Cost and Other Comprehensive Income (Loss)	7	25	(270)
United States | Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	2	2	2
Interest cost	196	218	63
Expected return on plan assets	(217)	(210)	(67)
Recognized net actuarial loss (gain)	27	24	22
Amortization of prior service credit	(2)	(2)	(2)
Recognized settlement loss	53	93	173
Recognized curtailment gain	0	0	0
Defined Benefit Plans	59	125	191
Defined contribution plans	1	26	37
Net Periodic Benefit Cost (Credit)	60	151	228
Net actuarial (gain) loss	(105)	243	(50)
Prior service cost (credit)	0	0	0
Amortization of net actuarial (loss) gain	(80)	(117)	(195)
Amortization of net prior service credit	2	2	2
Curtailment gain	0	0	0
Total Recognized in Other Comprehensive Income	(183)	128	(243)
Total Recognized in Net Periodic Benefit Cost and Other Comprehensive Income (Loss)	(123)	279	(15)
Foreign Plan | Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	20	22	27
Interest cost	113	153	149
Expected return on plan assets	(191)	(233)	(244)
Recognized net actuarial loss (gain)	58	43	56
Amortization of prior service credit	(1)	(2)	(4)
Recognized settlement loss	1	1	1
Recognized curtailment gain	(1)	0	(1)
Defined Benefit Plans	(1)	(16)	(16)
Defined contribution plans	18	23	29
Net Periodic Benefit Cost (Credit)	17	7	13
Net actuarial (gain) loss	(9)	24	33
Prior service cost (credit)	4	0	41
Amortization of net actuarial (loss) gain	(59)	(44)	(57)
Amortization of net prior service credit	1	2	4
Curtailment gain	1	0	1
Total Recognized in Other Comprehensive Income	(62)	(18)	22
Total Recognized in Net Periodic Benefit Cost and Other Comprehensive Income (Loss)	$ (45)	$ (11)	$ 35
United States of America, Dollars
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Out-of-period adjustment, gross				$ (53)