Reclassifications from Accumulated Other Comprehensive Income (Loss) (Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018		Dec. 31, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other income, net	$ 7	$ 0		$ (5)
Provision (benefit) for income taxes	(411)	1		(93)
Net income	(891)	$ (537)	[1]	$ (1,046)	[1]
Reclassified from Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income	8
Pension and Other Postretirement | Reclassified from Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other income, net	10
Provision (benefit) for income taxes	(2)
Net income	$ 8

[1] In 2018 and 2017, deferred tax activity incurred in other comprehensive income was offset by a valuation allowance.