Accumulated Other Comprehensive Income/(Loss) (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2021		Jun. 30, 2020		Jun. 30, 2021		Jun. 30, 2020
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	$ (1,594)		$ (1,329)		$ (1,593)		$ (1,356)
Other comprehensive income/(loss) before reclassifications	18		(60)		(9)		(53)
Amounts reclassified from accumulated other comprehensive income/(loss)	25		17		51		37
Net to-date other comprehensive income/(loss), net of taxes	43	[1]	(43)	[1]	42	[2]	(16)	[2]
Balance at June 30	(1,551)		(1,372)		(1,551)		(1,372)
Deferred taxes activity other comprehensive income/(loss)	(10)		(5)		(18)		(12)
Defined Benefit Plans [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	(1,356)		(1,128)		(1,381)		(1,150)
Other comprehensive income/(loss) before reclassifications	(1)		1		(2)		3
Amounts reclassified from accumulated other comprehensive income/(loss)	25		17		51		37
Net to-date other comprehensive income/(loss), net of taxes	24		18		49		40
Balance at June 30	(1,332)		(1,110)		(1,332)		(1,110)
Foreign Currency Translation [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	(238)		(201)		(212)		(206)
Other comprehensive income/(loss) before reclassifications	19		(61)		(7)		(56)
Net to-date other comprehensive income/(loss), net of taxes	19		(61)		(7)		(56)
Balance at June 30	$ (219)		$ (262)		$ (219)		$ (262)

[1] Net of deferred taxes of ($10) million and ($5) million during the three months ended June 30, 2021 and 2020, respectively.

[2] Net of deferred taxes of ($18) million and ($12) million during the six months ended June 30, 2021 and 2020, respectively.