Income Taxes - Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Deferred Tax Assets:
Net operating loss and tax credit carryforwards	$ 477	$ 599
Pension and postretirement benefits	86	112
Reserves not deductible until paid	14	20
Self insurance	2	2
Capitalized interest	7	13
Inventories	4	6
Share-based compensation	14	28
Other	7	4
Deferred tax assets before valuation allowance	611	784
Valuation allowance	(175)	(51)
Total deferred tax assets	436	733
Deferred Tax Liabilities:
Property, plant and equipment	153	245
Other	0	0
Total deferred tax liabilities	153	245
Net deferred tax assets	$ 283	$ 488