Acquisitions and Disposition - Allocation of the Aggregate Purchase Price Based on Estimated Fair Values (Details) - USD ($) $ in Millions	Jan. 15, 2021	Dec. 31, 2021	Dec. 31, 2020
Assets Acquired:
Goodwill		$ 920	$ 4
Big River Steel
Assets Acquired:
Receivables	$ 166
Receivables with U. S. Steel	99
Inventories	184
Other current assets	16
Property, plant and equipment	2,188
Intangibles	413
Goodwill	916
Other noncurrent assets	19
Total Assets Acquired	4,001
Liabilities Assumed:
Accounts payable and accrued liabilities	224
Payroll and benefits payable	27
Accrued taxes	9
Accrued interest	33
Short-term debt and current maturities of long-term debt	29
Long-term debt	1,997
Deferred income tax liabilities	26
Deferred credits and other long-term liabilities	211
Total Liabilities Assumed	2,556
Fair value of previously held investment in Big River Steel	770
Purchase price, including assumed liabilities and net of cash acquired	675
Difference in assets acquired and liabilities assumed	1,445
Receivables for payments made by Big River Steel on behalf of U. S. Steel for retention bonuses	22
Impact of retention bonuses on the previously held equity investment and for U. S. Steel liabilities assumed in the purchase	50
Assumed receivables for steel substrate sales from Big River Steel to U. S. Steel	$ 27