Pension and Other Postretirement Benefits - Schedule of Obligations and Funded Status (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Pension benefits
Change in benefit obligation
Benefit obligation at beginning of year	$ 6,476	$ 7,359
Service cost	25	46	$ 90
Interest cost	235	219	234
Amendments	0	18
Actuarial losses (gains)	974	(372)
Settlements	(23)	(146)
Curtailments	0	(154)
Benefits paid	(477)	(422)
Medicare Part D subsidy receipts	0	0
Foreign currency translation impact	39	(72)
Benefit obligation at end of year	7,249	6,476	7,359
Change in plan assets
Fair value of plan assets at beginning of year	4,334	4,862
Actual return on plan assets	731	(144)
Employer contributions	268	298
Benefits paid	(453)	(397)
Administrative expenses	(34)	(33)
Settlements	(22)	(178)
Foreign currency translation impact	44	(74)
Fair value of plan assets at end of year	4,868	4,334	4,862
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract]
Net funded status	(2,381)	(2,142)
Amounts recognized in the Consolidated Balance Sheet consist of:
Noncurrent assets	104	111
Current liabilities	(25)	(23)
Noncurrent liabilities	(2,460)	(2,230)
Net amount recognized	(2,381)	(2,142)
Amounts recognized in Accumulated Other Comprehensive Loss consist of:
Net actuarial loss	3,375	2,957
Prior service cost (benefit)	1	3
Net amount recognized, before tax effect	3,376	2,960
Other changes in plan assets and benefit obligations recognized in Other Comprehensive Loss consist of:
Net actuarial loss (gain)	566	(19)
Amortization of accumulated net actuarial loss	(148)	(264)
Prior service cost (benefit)	0	19
Amortization of prior service (cost) benefit	(2)	(26)
Net amount recognized, before tax effect	416	(290)
Other postretirement benefits
Change in benefit obligation
Benefit obligation at beginning of year	806	927
Service cost	7	7	7
Interest cost	28	28	30
Amendments	(78)	(25)
Actuarial losses (gains)	100	(51)
Settlements	0	0
Curtailments	0	0
Benefits paid	(82)	(86)
Medicare Part D subsidy receipts	5	6
Foreign currency translation impact	0	0
Benefit obligation at end of year	786	806	927
Change in plan assets
Fair value of plan assets at beginning of year	0	0
Actual return on plan assets	0	0
Employer contributions	0	0
Benefits paid	0	0
Administrative expenses	0	0
Settlements	0	0
Foreign currency translation impact	0	0
Fair value of plan assets at end of year	0	0	$ 0
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract]
Net funded status	(786)	(806)
Amounts recognized in the Consolidated Balance Sheet consist of:
Noncurrent assets	0	0
Current liabilities	(72)	(83)
Noncurrent liabilities	(714)	(723)
Net amount recognized	(786)	(806)
Amounts recognized in Accumulated Other Comprehensive Loss consist of:
Net actuarial loss	179	87
Prior service cost (benefit)	(37)	(27)
Net amount recognized, before tax effect	142	60
Other changes in plan assets and benefit obligations recognized in Other Comprehensive Loss consist of:
Net actuarial loss (gain)	100	(52)
Amortization of accumulated net actuarial loss	(8)	(7)
Prior service cost (benefit)	(78)	(25)
Amortization of prior service (cost) benefit	68	35
Net amount recognized, before tax effect	82	(49)
United States | Pension benefits
Change in benefit obligation
Benefit obligation at beginning of year	5,282
Benefit obligation at end of year	5,884	5,282
Change in plan assets
Fair value of plan assets at beginning of year	3,123
Fair value of plan assets at end of year	3,513	3,123
Other changes in plan assets and benefit obligations recognized in Other Comprehensive Loss consist of:
Funded status for U.S. pension plans	$ (2,371)	$ (2,159)