Stockholders' Equity (Components of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Net current period other comprehensive income (loss)		$ 78	$ 125	$ (137)	$ (274)
Net current period other comprehensive income (loss)		11	5	29	39
Defined Benefit Pension Plans
Defined benefit and other postretirement benefit plans - Beginning balance				(912)	(979)
Other comprehensive income/(loss) before reclassifications				1	22
(Income)/loss reclassified from AOCI	[1]			38	16
Net current period other comprehensive income (loss)				39	38
Defined benefit and other postretirement benefit plans - Ending balance		(873)	(941)	(873)	(941)
Other Postretirement Benefit Plans
Defined benefit and other postretirement benefit plans - Beginning balance				(40)	(13)
Other comprehensive income/(loss) before reclassifications				(12)	2
(Income)/loss reclassified from AOCI	[1]			0	(1)
Net current period other comprehensive income (loss)				(12)	1
Defined benefit and other postretirement benefit plans - Ending balance		(52)	(12)	(52)	(12)
Unrealized Translation
Unrealized translation - Beginning balance				(2,157)	(2,271)
Other comprehensive income/(loss) before reclassifications				(127)	(266)
(Income)/loss reclassified from AOCI				0	0
Net current period other comprehensive income (loss)				(127)	(266)
Unrealized translation - Ending balance		(2,284)	(2,537)	(2,284)	(2,537)
Cash Flow Hedges and Other
Cash flow hedge and other - Beginning balance				(63)	(31)
Other comprehensive income/(loss) before reclassifications				28	17
(Income)/loss reclassified from AOCI				29	(9)
Net current period other comprehensive income (loss)				57	8
Cash flow hedge and other - Ending balance		$ (6)	$ (23)	$ (6)	$ (23)

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