Stockholders' Equity (Components of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2021	Mar. 31, 2020
Net current period other comprehensive income (loss)		$ (215)	$ (399)
Net current period other comprehensive income (loss)		18	34
Defined Benefit Pension Plans
Defined benefit and other postretirement benefit plans - Beginning balance		(912)	(979)
Other comprehensive income/(loss) before reclassifications		0	19
(Income)/loss reclassified from AOCI	[1]	14	10
Net current period other comprehensive income (loss)		14	29
Defined benefit and other postretirement benefit plans - Ending balance		(898)	(950)
Other Postretirement Benefit Plans
Defined benefit and other postretirement benefit plans - Beginning balance		(40)	(13)
Other comprehensive income/(loss) before reclassifications		2	5
(Income)/loss reclassified from AOCI	[1]	0	0
Net current period other comprehensive income (loss)		2	5
Defined benefit and other postretirement benefit plans - Ending balance		(38)	(8)
Unrealized Translation
Unrealized translation - Beginning balance		(2,157)	(2,271)
Other comprehensive income/(loss) before reclassifications		(205)	(386)
(Income)/loss reclassified from AOCI		0	0
Net current period other comprehensive income (loss)		(205)	(386)
Unrealized translation - Ending balance		(2,362)	(2,657)
Cash Flow Hedges and Other
Cash flow hedge and other - Beginning balance		(63)	(31)
Other comprehensive income/(loss) before reclassifications		22	31
(Income)/loss reclassified from AOCI		12	0
Net current period other comprehensive income (loss)		34	31
Cash flow hedge and other - Ending balance		$ (29)	$ 0

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