Accumulated Other Comprehensive Loss - Schedule of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	Jan. 01, 2019
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Stockholders' equity attributable to parent, beginning balance			$ 10,249
Reclassification of tax effects per ASU 2018-02	$ 2,015		2,015		$ 1,792
Stockholders' equity attributable to parent, ending balance	10,335		10,335
Foreign currency translation [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Stockholders' equity attributable to parent, beginning balance	(746)	$ (607)	(538)	$ (616)
Other comprehensive income/(loss) before reclassifications	48	(19)	(160)	(10)
Amounts reclassified from accumulated other comprehensive income/(loss) (net of income tax)	0	0	0	0
Net current-period other comprehensive income/(loss)	48	(19)	(160)	(10)
Stockholders' equity attributable to parent, ending balance	(698)	(626)	(698)	(626)
Foreign currency translation [Member] | Accounting Standards Update 2018-02 [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Reclassification of tax effects per ASU 2018-02	0	0	0	0
Derivative instruments [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Stockholders' equity attributable to parent, beginning balance	(5)	3	13	(8)
Other comprehensive income/(loss) before reclassifications	(3)	(7)	(22)	(1)
Amounts reclassified from accumulated other comprehensive income/(loss) (net of income tax)	2	0	3	5
Net current-period other comprehensive income/(loss)	(1)	(7)	(19)	4
Stockholders' equity attributable to parent, ending balance	(6)	(4)	(6)	(4)
Derivative instruments [Member] | Accounting Standards Update 2018-02 [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Reclassification of tax effects per ASU 2018-02	0	0	0	0
Defined pension and post-retirement benefit costs [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Stockholders' equity attributable to parent, beginning balance	(1,695)	(1,370)	(1,702)	(1,337)
Other comprehensive income/(loss) before reclassifications	6	3	2	4
Amounts reclassified from accumulated other comprehensive income/(loss) (net of income tax)	3	4	14	6
Net current-period other comprehensive income/(loss)	9	7	16	10
Stockholders' equity attributable to parent, ending balance	(1,686)	(1,363)	(1,686)	(1,363)
Defined pension and post-retirement benefit costs [Member] | Accounting Standards Update 2018-02 [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Reclassification of tax effects per ASU 2018-02	0	(36)	0	(36)		$ 36
Total [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Stockholders' equity attributable to parent, beginning balance	(2,446)	(1,974)	(2,227)	(1,961)
Other comprehensive income/(loss) before reclassifications	51	(23)	(180)	(7)
Amounts reclassified from accumulated other comprehensive income/(loss) (net of income tax)	5	4	17	11
Net current-period other comprehensive income/(loss)	56	(19)	(163)	4
Stockholders' equity attributable to parent, ending balance	(2,390)	(1,993)	(2,390)	(1,993)
Total [Member] | Accounting Standards Update 2018-02 [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Reclassification of tax effects per ASU 2018-02	$ 0	$ (36)	$ 0	$ (36)