Reclassifications Out of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other net periodic benefit costs	$ 5	$ (3)
Net interest and other	(49)	(45)
Income (loss) before income taxes	27	524
(Provision) benefit for income taxes(a)	147	(168)
Net income	174	356
Reclassification out of Accumulated Other Comprehensive Income (Loss)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income (loss) before income taxes	4	(3)
(Provision) benefit for income taxes(a)	0	0
Net income	4	(3)
Amortization of prior service credit | Reclassification out of Accumulated Other Comprehensive Income (Loss)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other net periodic benefit costs	6	4
Amortization of actuarial loss | Reclassification out of Accumulated Other Comprehensive Income (Loss)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other net periodic benefit costs	(2)	(3)
Net settlement loss | Reclassification out of Accumulated Other Comprehensive Income (Loss)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other net periodic benefit costs	0	(4)
Pension Benefits
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other net periodic benefit costs	$ 0	$ (4)