Employee Benefit Plans - Total Recognized in Net Periodic Benefit Cost and Other Comprehensive Income (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018		Dec. 31, 2017	Dec. 31, 2016	Sep. 30, 2018
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plans		$ 175		$ 194	$ 127
Net actuarial (gain) loss(4)		273		52	(118)
Amortization of net actuarial loss	[1]	(252)		(236)	(160)
Amortization of net prior service credit	[1]	(26)		(10)	(10)
Total Recognized in Other Comprehensive Income (Loss)(5)		(540)		(169)	(141)
Interest expense on non-TRA obligations		258		257	296
Interest (income) expense allocated to TRA participant accounts		(46)		127	83
Expected Investment Income on Non-TRA Assets		(357)		321	356
Actual investment (loss) income on TRA assets		(46)		127	83
Pension Plan [Member] | Benefit plans net actuarial (loss) gain [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Pension and Other Postretirement Benefit Plans, Amounts that Will be Amortized from Accumulated Other Comprehensive Income (Loss) in Next Fiscal Year		(63)
Pension Plan [Member] | Benefit plans prior service credits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Pension and Other Postretirement Benefit Plans, Amounts that Will be Amortized from Accumulated Other Comprehensive Income (Loss) in Next Fiscal Year		4
Other Postretirement Benefits Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost		4		5	6
Interest cost	[2]	23		28	32
Expected return on plan assets	[3]	0		0	0
Recognized net actuarial loss		0		1	2
Amortization of prior service credit		(19)		(4)	(5)
Recognized settlement loss		0		0	0
Recognized curtailment gain		0		0	0
Defined Benefit Plans		8		30	35
Net Periodic Benefit Cost		8		30	35
Net actuarial (gain) loss(4)		(63)		(16)	(75)
Prior service cost (credit)		(234)		0	0
Amortization of net actuarial loss		0		(1)	(2)
Amortization of net prior service credit		19		4	5
Curtailment gain		0		0	0
Total Recognized in Other Comprehensive Income (Loss)(5)	[4]	(278)		(13)	(72)
Total Recognized in Net Periodic Benefit Cost and Other Comprehensive Income (Loss)		(270)		17	(37)
Other Postretirement Benefits Plan [Member] | Benefit plans net actuarial (loss) gain [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Pension and Other Postretirement Benefit Plans, Amounts that Will be Amortized from Accumulated Other Comprehensive Income (Loss) in Next Fiscal Year		3
Other Postretirement Benefits Plan [Member] | Benefit plans prior service credits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Pension and Other Postretirement Benefit Plans, Amounts that Will be Amortized from Accumulated Other Comprehensive Income (Loss) in Next Fiscal Year		76
U.S. | Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost		2		2	4
Interest cost	[2]	63		226	184
Expected return on plan assets	[3]	(67)		(227)	(190)
Recognized net actuarial loss		22		21	26
Amortization of prior service credit		(2)		(2)	(2)
Recognized settlement loss		173		133	65
Recognized curtailment gain		0		0	0
Defined Benefit Plans		191		153	87
Defined contribution plans	[5]	37		38	43
Net Periodic Benefit Cost		228		191	130
Net actuarial (gain) loss(4)		(50)		238	84
Prior service cost (credit)		0		0	0
Amortization of net actuarial loss		(195)		(154)	(92)
Amortization of net prior service credit		2		2	2
Curtailment gain		0		0	0
Total Recognized in Other Comprehensive Income (Loss)(5)	[4]	(243)		86	(6)
Total Recognized in Net Periodic Benefit Cost and Other Comprehensive Income (Loss)		(15)		277	124
Foreign Plan [Member] | Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost		27		29	31
Interest cost	[2]	149		158	195
Expected return on plan assets	[3]	(244)		(221)	(249)
Recognized net actuarial loss		56		79	65
Amortization of prior service credit		(4)		(4)	(3)
Recognized settlement loss		1		2	1
Recognized curtailment gain		(1)		(2)	0
Defined Benefit Plans		(16)		41	40
Defined contribution plans	[5]	29		29	31
Net Periodic Benefit Cost		13		70	71
Net actuarial (gain) loss(4)		33	[6]	(273)	76
Prior service cost (credit)		41		(1)	0
Amortization of net actuarial loss		(57)		(81)	(66)
Amortization of net prior service credit		4		4	3
Curtailment gain		1		0	0
Total Recognized in Other Comprehensive Income (Loss)(5)	[4]	22		(351)	13
Total Recognized in Net Periodic Benefit Cost and Other Comprehensive Income (Loss)		$ 35		$ (281)	$ 84
United States of America, Dollars
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Out-of-Period Adjustment, Gross						$ (53)

[1] Reclassified to Total Net Periodic Benefit Cost - refer to Note 17 - Employee Benefit Plans for additional information.

[2] Interest cost for Pension Benefits includes interest expense on non-TRA obligations of $258, $257 and $296 and interest (income) expense directly allocated to TRA participant accounts of $(46), $127 and $83 for the years ended December 31, 2018, 2017 and 2016, respectively.

[3] Expected return on plan assets includes expected investment (loss) income on non-TRA assets of $(357), $321 and $356 and actual investment (loss) income on TRA assets of $(46), $127 and $83 for the years ended December 31, 2018, 2017 and 2016, respectively.

[4] Amounts represent the pre-tax effect included in Other Comprehensive Income (Loss). Refer to Note 23 - Other Comprehensive Income (Loss) for the related tax effects and the net of tax amounts.

[5] Prior year amounts have been revised to reflect additional cost for previously excluded plans.

[6] The non-U.S. plans Net actuarial (gain) loss for 2018 reflects an out-of-period adjustment in third quarter 2018 of $(53) to correct an overstated benefit obligation for our U.K. Final Salary Pension Plan at December 31, 2017. Refer to Note 1 - Basis of Presentation and Summary of Significant Accounting Policies for additional information regarding this adjustment.