Other Comprehensive Loss - Reclassified from Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reclassification from accumulated other comprehensive loss
Amortization of pension and other postretirement benefits									$ 8	$ 6	$ 39
(Loss) income from continuing operations before income taxes									(20)	(165)	186
Income tax (expense) benefit									(150)	8	(50)
Net (loss) income	$ (173)	$ (17)	$ 22	$ (2)	$ (69)	$ (366)	$ 198	$ 80	(170)	(157)	$ 144
Reclassification out of Accumulated Other Comprehensive Income
Reclassification from accumulated other comprehensive loss
Income tax (expense) benefit									0	0
Net (loss) income									15	18
Reclassification out of Accumulated Other Comprehensive Income | Actuarial loss
Reclassification from accumulated other comprehensive loss
Amortization of pension and other postretirement benefits									14	15
Reclassification out of Accumulated Other Comprehensive Income | Prior service cost
Reclassification from accumulated other comprehensive loss
Amortization of pension and other postretirement benefits									1	3
Reclassification out of Accumulated Other Comprehensive Income | Pension and other postretirement benefits adjustments, net of tax
Reclassification from accumulated other comprehensive loss
(Loss) income from continuing operations before income taxes									$ 15	$ 18