Divestitures and Held for Sale - Schedule of Assets and Liabilities Classified as Held for Sale in Consolidated Balance Sheet (Detail) $ in Millions	Dec. 31, 2020 USD ($)
Assets
Total current assets	$ 648
Liabilities
Total current liabilities	242
Held for Sale [Member]
Assets
Total Assets held for sale	648
Liabilities
Total Liabilities held for sale	242
Held for Sale [Member] | Warrick Rolling Mill [Member]
Assets
Receivables from customers	86
Other receivables	6
Inventories	164
Total current assets	256
Properties, plants, and equipment	1,423
Accumulated depreciation	(1,031)
Properties, plants, and equipment, net	392
Total Assets held for sale	648
Liabilities
Accounts payable, trade	121
Accrued compensation and retirement costs	5
Other current liabilities	25
Total current liabilities	151
Accrued other postretirement benefits	83
Other noncurrent liabilities	8
Total Liabilities held for sale	$ 242