Stockholders' Equity (Components of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Net current period other comprehensive income (loss)		$ 38	$ (170)	$ (236)	$ (148)
Net current period other comprehensive income (loss)		0	16	39	38
Defined Benefit Pension Plans
Defined benefit and other postretirement benefit plans - Beginning balance				(979)	(1,017)
Other comprehensive income/(loss) before reclassifications				(19)	1
(Income)/loss reclassified from AOCI	[1]			57	22
Net current period other comprehensive income (loss)				38	23
Defined benefit and other postretirement benefit plans - Ending balance		(941)	(994)	(941)	(994)
Other Postretirement Benefit Plans
Defined benefit and other postretirement benefit plans - Beginning balance				(13)	12
Other comprehensive income/(loss) before reclassifications				3	16
(Income)/loss reclassified from AOCI	[1]			(1)	(1)
Net current period other comprehensive income (loss)				2	15
Defined benefit and other postretirement benefit plans - Ending balance		(11)	27	(11)	27
Unrealized Translation
Unrealized translation - Beginning balance				(2,271)	(2,297)
Other comprehensive income/(loss) before reclassifications				(233)	(132)
(Income)/loss reclassified from AOCI				0	0
Net current period other comprehensive income (loss)				(233)	(132)
Unrealized translation - Ending balance		(2,504)	(2,429)	(2,504)	(2,429)
Cash Flow Hedges and Other
Cash flow hedge and other - Beginning balance				(31)	3
Other comprehensive income/(loss) before reclassifications				15	(6)
(Income)/loss reclassified from AOCI				(10)	(13)
Net current period other comprehensive income (loss)				5	(19)
Cash flow hedge and other - Ending balance		$ (26)	$ (16)	$ (26)	$ (16)

[1] Included in computation of net periodic benefit costs.