United States Steel (X) 10-Q 29 Oct 21 2021 Q3 Quarterly report Financial data

Cover Page

Cover Page - shares	9 Months Ended
	Sep. 30, 2021	Oct. 25, 2021
Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2021
Document Transition Report	false
Entity File Number	1-16811
Entity Registrant Name	United States Steel Corp
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	25-1897152
Entity Address, Address Line One	600 Grant Street,
Entity Address, City or Town	Pittsburgh,
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	15219-2800
City Area Code	412
Local Phone Number	433-1121
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		270,232,763
Amendment Flag	false
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
Entity Central Index Key	0001163302
Current Fiscal Year End Date	--12-31
New York Stock Exchange
Entity Information [Line Items]
Title of 12(b) Security	United States Steel Corporation Common Stock
Trading Symbol	X
Security Exchange Name	NYSE
Chicago Stock Exchange
Entity Information [Line Items]
Title of 12(b) Security	United States Steel Corporation Common Stock
Trading Symbol	X
Security Exchange Name	CHX

CONSOLIDATED STATEMENT OF OPERA

CONSOLIDATED STATEMENT OF OPERATIONS (Unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Net sales:
Net sales	$ 5,623	$ 2,072	$ 13,676	$ 6,469
Net sales to related parties (Note 19)	341	268	977	710
Total (Note 6)	5,964	2,340	14,653	7,179
Operating expenses (income):
Cost of sales	3,881	2,295	10,633	7,174
Selling, general and administrative expenses	108	65	316	199
Depreciation, depletion and amortization	196	162	587	481
(Earnings) loss from investees	(57)	31	(106)	78
Gain on sale of Transtar (Note 5)	(506)	0	(506)	0
Asset impairment charges (Note 1)	0	0	28	263
Gain on equity investee transactions	0	0	(111)	(31)
Restructuring and other charges (Note 20)	0	0	37	130
Net gain on sale of assets	7	(2)	(8)	(2)
Other (gains) losses, net	(7)	0	(18)	5
Total	3,622	2,551	10,852	8,297
Earnings (loss) before interest and income taxes	2,342	(211)	3,801	(1,118)
Interest expense	75	84	251	198
Interest income	(1)	(1)	(3)	(6)
Loss on debt extinguishment	26	0	282	0
Other financial costs (benefits)	17	(30)	39	(26)
Net periodic benefit income	(37)	(6)	(97)	(22)
Net interest and other financial costs	80	47	472	144
Earnings (loss) before income taxes	2,262	(258)	3,329	(1,262)
Income tax expense (benefit) (Note 12)	260	(24)	224	(48)
Net earnings (loss)	2,002	(234)	3,105	(1,214)
Less: Net earnings attributable to noncontrolling interests	0	0	0	0
Net earnings (loss) attributable to United States Steel Corporation	$ 2,002	$ (234)	$ 3,105	$ (1,214)
Earnings (loss) per share attributable to United States Steel Corporation stockholders:
-Basic (in dollars per share)	$ 7.41	$ (1.06)	$ 11.80	$ (6.43)
-Diluted (in dollars per share)	$ 6.97	$ (1.06)	$ 11.13	$ (6.43)

CONSOLIDATED STATEMENT OF COMPR

CONSOLIDATED STATEMENT OF COMPREHENSIVE INCOME (LOSS) (Unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Statement of Comprehensive Income [Abstract]
Net earnings (loss)	$ 2,002	$ (234)	$ 3,105	$ (1,214)
Other comprehensive income (loss), net of tax:
Changes in foreign currency translation adjustments	(26)	34	(50)	31
Changes in pension and other employee benefit accounts	15	16	244	97
Changes in derivative financial instruments	60	8	9	18
Total other comprehensive income, net of tax	49	58	203	146
Comprehensive income (loss) including noncontrolling interest	2,051	(176)	3,308	(1,068)
Comprehensive income attributable to noncontrolling interest	0	0	0	0
Comprehensive income (loss) attributable to United States Steel Corporation	$ 2,051	$ (176)	$ 3,308	$ (1,068)

CONSOLIDATED BALANCE SHEET (Una

CONSOLIDATED BALANCE SHEET (Unaudited) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents (Note 7)	$ 2,044	$ 1,985
Receivables, less allowance of $43 and $34	2,275	914
Receivables from related parties (Note 19)	128	80
Inventories (Note 8)	2,086	1,402
Other current assets	266	51
Total current assets	6,799	4,432
Long-term restricted cash (Note 7)	91	130
Operating lease assets	198	214
Property, plant and equipment	19,880	17,704
Less accumulated depreciation and depletion	12,500	12,260
Total property, plant and equipment, net	7,380	5,444
Investments and long-term receivables, less allowance of $4 and $5	628	1,177
Intangibles, net (Note 9)	527	129
Deferred income tax benefits (Note 12)	46	22
Goodwill (Note 9)	909	4
Other noncurrent assets	755	507
Total assets	17,333	12,059
Current liabilities:
Accounts payable and other accrued liabilities	2,870	1,779
Accounts payable to related parties (Note 19)	130	105
Payroll and benefits payable	542	308
Accrued taxes	315	154
Accrued interest	52	59
Current operating lease liabilities	60	59
Short-term debt and current maturities of long-term debt (Note 15)	61	192
Total current liabilities	4,030	2,656
Noncurrent operating lease liabilities	148	163
Long-term debt, less unamortized discount and debt issuance costs (Note 15)	4,272	4,695
Employee benefits	202	322
Deferred income tax liabilities (Note 12)	200	11
Deferred credits and other noncurrent liabilities	473	333
Total liabilities	9,325	8,180
Contingencies and commitments (Note 21)
Stockholders’ Equity (Note 17):
Common stock (279,350,782 and 229,105,589 shares issued) (Note 13)	279	229
Treasury stock, at cost (9,133,393 shares and 8,673,131 shares)	(184)	(175)
Additional paid-in capital	5,185	4,402
Retained earnings (accumulated deficit)	2,480	(623)
Accumulated other comprehensive income (loss) (Note 18)	156	(47)
Total United States Steel Corporation stockholders’ equity	7,916	3,786
Noncontrolling interests	92	93
Total liabilities and stockholders’ equity	$ 17,333	$ 12,059

CONSOLIDATED BALANCE SHEET (U_2

CONSOLIDATED BALANCE SHEET (Unaudited) (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Receivables, allowance	$ 43	$ 34
Investments and long-term receivables, allowance	$ 4	$ 5
Common stock, shares issued (in shares)	279,350,782	229,105,589
Treasury stock, shares (in shares)	9,133,393	8,673,131

CONSOLIDATED STATEMENT OF CASH

CONSOLIDATED STATEMENT OF CASH FLOWS (Unaudited) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Operating activities:
Net earnings (loss)	$ 3,105	$ (1,214)
Adjustments to reconcile to net cash provided by operating activities:
Depreciation, depletion and amortization	587	481
Gain on sale of Transtar (Note 5)	(506)	0
Asset impairment charges (Note 1)	28	263
Gain on equity investee transactions	(111)	(31)
Restructuring and other charges (Note 20)	37	130
Loss on debt extinguishment	282	0
Pensions and other postretirement benefits	(88)	(18)
Deferred income taxes (Note 12)	59	(36)
Net gain on sale of assets	(8)	(2)
Equity investee (earnings) loss, net of distributions received	(106)	78
Changes in:
Current receivables	(1,281)	(18)
Inventories	(539)	495
Current accounts payable and accrued expenses	968	(267)
Income taxes receivable/payable	137	13
All other, net	41	(23)
Net cash provided by (used in) operating activities	2,605	(149)
Investing activities:
Capital expenditures	(460)	(591)
Acquisition of Big River Steel, net of cash acquired (Note 5)	(625)	0
Investment in Big River Steel	0	(3)
Proceeds from sale of Transtar (Note 5)	627	0
Proceeds from sale of assets	25	3
Proceeds from sale of ownership interests in equity investees	0	8
Other investing activities	3	4
Net cash used in investing activities	(436)	(587)
Financing activities:
Issuance of short-term debt, net of financing costs (Note 15)	0	240
Repayment of short-term debt (Note 15)	(180)	0
Revolving credit facilities - borrowings, net of financing costs (Note 15)	50	1,474
Revolving credit facilities - repayments (Note 15)	(911)	(1,633)
Issuance of long-term debt, net of financing costs (Note 15)	862	1,043
Repayment of long-term debt (Note 15)	(2,719)	(8)
Proceeds from public offering of common stock (Note 22)	790	410
Proceeds from Stelco Option Agreement	0	55
Other financing activities	(12)	(7)
Net cash (used in) provided by financing activities	(2,120)	1,574
Effect of exchange rate changes on cash	(15)	10
Net increase in cash, cash equivalents and restricted cash	34	848
Cash, cash equivalents and restricted cash at beginning of year (Note 7)	2,118	939
Cash, cash equivalents and restricted cash at end of period (Note 7)	2,152	1,787
Noncash Investing and Financing Items [Abstract]
Change in accrued capital expenditures	58	(109)
U. S. Steel common stock issued for employee/non-employee director stock plans	28	18
Capital expenditures funded by finance lease borrowings	11	30
Export Credit Agreement (ECA) financing	$ 23	$ 34

Basis of Presentation and Signi

Basis of Presentation and Significant Accounting Policies	9 Months Ended
	Sep. 30, 2021
Accounting Policies [Abstract]
Basis of Presentation and Significant Accounting Policies	1. Basis of Presentation and Significant Accounting Policies The year-end Consolidated Balance Sheet data was derived from audited statements but does not include all disclosures required for complete financial statements by accounting principles generally accepted in the United States of America (U.S. GAAP). The other information in these condensed financial statements is unaudited but, in the opinion of management, reflects all adjustments necessary for a fair statement of the results for the periods covered, including assessment of certain accounting matters using all available information including consideration of forecasted financial information in context with other information reasonably available to us. However, our future assessment of our current expectations, including consideration of the unknown future impacts of the COVID-19 pandemic, could result in material impacts to our consolidated financial statements in future reporting periods. All such adjustments are of a normal recurring nature unless disclosed otherwise. These condensed financial statements, including notes, have been prepared in accordance with the applicable rules of the Securities and Exchange Commission and do not include all of the information and disclosures required by U.S. GAAP for complete financial statements. Additional information is contained in the United States Steel Corporation Annual Report on Form 10-K for the fiscal year ended December 31, 2020, which should be read in conjunction with these condensed financial statements. Asset Impairment In May 2019, U. S. Steel announced that it planned to construct a new endless casting and rolling facility at its Edgar Thomson Plant in Braddock, Pennsylvania, and a cogeneration facility at its Clairton Plant in Clairton, Pennsylvania, both part of the Company's Mon Valley Works. The Company purchased certain equipment for this project before delaying groundbreaking in March 2020 in response to COVID-19. In April 2021, the Company determined not to pursue this project and is re-evaluating uses for the already purchased equipment, including at the Company's recently announced potential mini mill investment. An impairment of $28 million was recognized for this project during the three-month period ended June 30, 2021.

New Accounting Standards

New Accounting Standards	9 Months Ended
	Sep. 30, 2021
Accounting Changes and Error Corrections [Abstract]
New Accounting Standards	New Accounting Standards In August 2020, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update 2020-06, Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity (ASU 2020-06). ASU 2020-06 simplifies the accounting for certain financial instruments with characteristics of liabilities and equity, including convertible instruments and contracts on an entity’s own equity. ASU 2020-06 requires entities to provide expanded disclosures about the terms and features of convertible instruments and amends certain guidance in ASC 260 on the computation of EPS for convertible instruments and contracts on an entity’s own equity. ASU 2020-06 is effective for public companies for fiscal years beginning after December 15, 2021, and interim periods within those fiscal years, with early adoption of all amendments in the same period permitted. The Company is continuing to assess the impact of adoption of the ASU. In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740) - Simplifying the Accounting for Income Taxes (ASU 2019-12). ASU 2019-12 simplifies accounting for income taxes by removing certain exceptions from the general principles in Topic 740 including elimination of the exception to the incremental approach for intraperiod tax allocation when there is a loss from continuing operations and income or a gain from other items such as other comprehensive income. U. S. Steel adopted this guidance on January 1, 2021. The adoption of this guidance did not have a material impact on the Company's Condensed Consolidated Financial Statements.

Recently Adopted Accounting Sta

Recently Adopted Accounting Standards	9 Months Ended
	Sep. 30, 2021
Accounting Standards Update and Change in Accounting Principle [Abstract]
Recently Adopted Accounting Standards	New Accounting Standards In August 2020, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update 2020-06, Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity (ASU 2020-06). ASU 2020-06 simplifies the accounting for certain financial instruments with characteristics of liabilities and equity, including convertible instruments and contracts on an entity’s own equity. ASU 2020-06 requires entities to provide expanded disclosures about the terms and features of convertible instruments and amends certain guidance in ASC 260 on the computation of EPS for convertible instruments and contracts on an entity’s own equity. ASU 2020-06 is effective for public companies for fiscal years beginning after December 15, 2021, and interim periods within those fiscal years, with early adoption of all amendments in the same period permitted. The Company is continuing to assess the impact of adoption of the ASU. In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740) - Simplifying the Accounting for Income Taxes (ASU 2019-12). ASU 2019-12 simplifies accounting for income taxes by removing certain exceptions from the general principles in Topic 740 including elimination of the exception to the incremental approach for intraperiod tax allocation when there is a loss from continuing operations and income or a gain from other items such as other comprehensive income. U. S. Steel adopted this guidance on January 1, 2021. The adoption of this guidance did not have a material impact on the Company's Condensed Consolidated Financial Statements.

Segment Information

Segment Information	9 Months Ended
	Sep. 30, 2021
Segment Reporting [Abstract]
Segment Information	4. Segment Information U. S. Steel has four reportable segments: North American Flat-Rolled (Flat-Rolled), Mini Mill, U. S. Steel Europe (USSE); and Tubular Products (Tubular). The Mini Mill segment reflects the acquisition of Big River Steel after the purchase of the remaining equity interest on January 15, 2021. See Note 5 for further details. Prior to the purchase, the equity earnings of Big River Steel were included in the Other segment. The Tubular Products segment includes the newly constructed electric arc furnace at our Fairfield Tubular Operations in Fairfield, Alabama. The results of our real estate business, the previously held equity method investment in Big River Steel, and of our former railroad business are combined and disclosed in the Other category. The results of segment operations for the three months ended September 30, 2021 and 2020 are: (In millions) Three Months Ended September 30, 2021 Customer Intersegment Net Earnings (loss) Earnings (loss) before interest and income taxes Flat-Rolled $ 3,541 $ 36 $ 3,577 $ 53 $ 1,015 Mini Mill 949 156 1,105 — 424 USSE 1,246 2 1,248 — 394 Tubular 216 6 222 4 — Total reportable segments 5,952 200 6,152 57 1,833 Other 12 9 21 — (2) Reconciling Items and Eliminations — (209) (209) — 511 Total $ 5,964 $ — $ 5,964 $ 57 $ 2,342 Three Months Ended September 30, 2020 Flat-Rolled $ 1,728 $ 71 $ 1,799 $ (3) $ (159) USSE 495 1 496 — 13 Tubular 96 — 96 — (52) Total reportable segments 2,319 72 2,391 (3) (198) Other 21 23 44 (28) (13) Reconciling Items and Eliminations — (95) (95) — — Total $ 2,340 $ — $ 2,340 $ (31) $ (211) The results of segment operations for the nine months ended September 30, 2021 and 2020 are: (In millions) Nine Months Ended September 30, 2021 Customer Intersegment Net Earnings (Loss) Earnings (loss) before interest and income taxes Flat-Rolled $ 8,804 $ 142 $ 8,946 $ 90 $ 1,740 Mini Mill 2,158 360 2,518 — 840 USSE 3,122 4 3,126 — 706 Tubular 534 13 547 10 (29) Total reportable segments 14,618 519 15,137 100 3,257 Other 35 65 100 6 20 Reconciling Items and Eliminations — (584) (584) — 524 Total $ 14,653 $ — $ 14,653 $ 106 $ 3,801 Nine Months Ended September 30, 2020 Flat-Rolled $ 5,199 $ 175 $ 5,374 $ (15) $ (523) USSE 1,403 3 1,406 — (27) Tubular 533 6 539 3 (147) Total reportable segments 7,135 184 7,319 (12) (697) Other 44 70 114 (66) (33) Reconciling Items and Eliminations — (254) (254) — (388) Total $ 7,179 $ — $ 7,179 $ (78) $ (1,118) A summary of total assets by segment is as follows: (In millions) September 30, 2021 December 31, 2020 Flat-Rolled $ 7,846 $ 7,099 Mini Mill 4,314 — USSE 6,116 5,502 Tubular 1,041 887 Total reportable segments $ 19,317 $ 13,488 Other $ 135 $ 911 Corporate, reconciling items, and eliminations (a) (2,119) (2,340) Total assets $ 17,333 $ 12,059 (a) The majority of Corporate, reconciling items, and eliminations total assets is comprised of cash and the elimination of intersegment amounts. The following is a schedule of reconciling items to consolidated earnings before interest and income taxes: Three Months Ended September 30, Nine Months Ended September 30, (In millions) 2021 2020 2021 2020 Items not allocated to segments: Gain on previously held investment in Big River Steel $ — $ — $ 111 $ — Big River Steel - inventory step-up amortization — — (24) — Big River Steel - unrealized gains (losses) (a) 12 — (3) — Big River Steel - acquisition costs — — (9) — Gain on sale of Transtar (Note 5) 506 — 506 — Loss on USSE assets held for sale (7) — (7) — Restructuring and other charges (Note 20) — — (37) (130) Asset impairment charges (Note 1) — — (28) (263) Property Sale — — 15 — Gain on previously held investment in UPI — — — 25 Tubular inventory impairment charge — — — (24) December 24, 2018 Clairton coke making facility fire — — — 4 Total reconciling items $ 511 $ — $ 524 $ (388) (a) Big River Steel – unrealized losses represent the post-acquisition mark-to-market impacts of hedging instruments acquired with the purchase of the remaining equity interest in Big River Steel on January 15, 2021. See Note 14 for further details.

Acquisition

Acquisition	9 Months Ended
	Sep. 30, 2021
Business Combinations [Abstract]
Acquisition	5. Acquisitions and Disposition Transtar Disposition On July 28, 2021, U. S. Steel completed the sale of 100 percent of its equity interests in its wholly-owned short-line railroad, Transtar, LLC (Transtar) to an affiliate of Fortress Transportation and Infrastructure Investors, LLC. The Company received net cash proceeds of $627 million, subject to certain customary adjustments as set forth in the Membership Interest Purchase Agreement, and recognized a pretax gain of approximately $506 million in the third quarter 2021. In connection with the closing of the transaction, the Company entered into certain ancillary agreements including a railway services agreement, providing for continued rail services for its Gary and Mon Valley Works facilities, and a transition services agreement. Because Transtar does not represent a significant component of U. S. Steel's business and does not constitute a reportable business segment, its results through the date of disposition are reported in the Other category. See Note 4 for further details. Big River Steel Acquisition On January 15, 2021, U. S. Steel purchased the remaining equity interest in Big River Steel for approximately $625 million in cash net of $36 million and $62 million in cash and restricted cash received, respectively, and the assumption of liabilities of approximately $50 million. There were acquisition related costs of approximately $9 million during the nine months ended September 30, 2021. Prior to the closing of the acquisition on January 15, 2021, U. S. Steel accounted for its 49.9% equity interest in Big River Steel under the equity method as control and risk of loss were shared among the partnership members. Using step acquisition accounting the Company increased the value of its previously held equity investment to its fair value of $770 million which resulted in a gain of approximately $111 million. The gain was recorded in gain on equity investee transactions in the Condensed Consolidated Statement of Operations. The acquisition has been accounted for in accordance with ASC 805, Business combinations . There were step-ups to fair value of approximately $308 million, $194 million and $24 million for property, plant and equipment, debt and inventory, respectively. An intangible asset for customer relationships and goodwill of approximately $413 million and $905 million were also recorded, respectively. Goodwill represents the excess of purchase price over the fair market value of the net assets. Goodwill is primarily attributable to Big River Steel's operational abilities, workforce and the anticipated benefits from their recent expansion and will be partially tax deductible. The inventory step-up was fully amortized as of March 31, 2021, the intangible asset will be amortized over a 22-year period and the debt step-up will be amortized over the contractual life of the underlying debt. See Note 15 for further details. The value of Big River Steel was determined using Level 3 valuation techniques. Level 3 valuation techniques include inputs to the valuation methodology that are considered unobservable and significant to the fair value measurement. A significant factor in determining the equity value was the discounted forecasted cash flows of Big River Steel. Forecasted cash flows are primarily impacted by the forecasted market price of steel and metallic inputs as well as the expected timing of significant capital expenditures. The model utilized a risk adjusted discount rate of 11.0% and a terminal growth rate of 2%. The following table presents the preliminary allocation of the aggregate purchase price based on estimated fair values: (in millions) Assets Acquired: Receivables $ 166 Receivables with U. S. Steel (1) 99 Inventories 184 Other current assets 16 Property, plant and equipment 2,188 Intangibles 413 Goodwill 905 Other noncurrent assets 19 Total Assets Acquired $ 3,990 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 44 Deferred credits and other long-term liabilities 182 Total Liabilities Assumed $ 2,545 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 (1) The transaction to purchase Big River Steel included receivables for payments made by Big River Steel on behalf of U. S. Steel for retention bonuses of $22 million that impacted the previously held equity investment and for U. S. Steel liabilities assumed in the purchase of approximately $50 million. In addition, there were assumed receivables of approximately $27 million for steel substrate sales from Big River Steel to U. S. Steel. The receivables with U. S. Steel eliminate in consolidation with offsetting intercompany payables from U. S. Steel. U. S. Steel is continuing to conform accounting policies and procedures and evaluate assets and liabilities assumed. During the one-year measurement period, we will continue to obtain information to assist in finalizing the fair value of assets acquired and liabilities assumed, which may differ materially from these preliminary estimates. The final purchase price allocation may include changes in allocations to intangible assets, such as customer relationships, as well as goodwill, changes to the fair value of long-term debt and other changes to assets and liabilities. We will apply any material adjustments in the reporting period in which the adjustments are determined. The following unaudited pro forma information for U. S. Steel includes the results of the Big River Steel acquisition as if it had been consummated on January 1, 2020. The unaudited pro forma information is based on historical information and is adjusted for amortization of the intangible asset, property, plant and equipment and debt fair value step-ups discussed above. Non-recurring acquisition related items included in the 2020 period include $111 million for the gain on previously held equity investment, $9 million in acquisition related costs and $24 million in inventory step-up amortization related to the purchase of the remaining interest in Big River Steel. In addition, costs for non-recurring retention bonuses of $44 million that occurred in January 2021 prior to the purchase of the remaining equity interest are included in the 2020 period. The pro forma information does not include any anticipated cost savings or other effects of the integration of Big River Steel. Accordingly, the unaudited pro forma information does not necessarily reflect the actual results that would have occurred, nor is it necessarily indicative of future results of operations. Pro forma adjustments were not tax-effected in 2020 as U. S. Steel had a full valuation allowance on its domestic deferred tax assets. Nine Months Ended September 30, (in millions) 2021 2020 Net sales $ 14,725 $ 7,849 Net earnings (loss) $ 3,034 $ (1,292) USS-POSCO Industries (UPI) Acquisition On February 29, 2020, U. S. Steel purchased the remaining equity interest in USS-POSCO Industries (UPI) that it did not already own, now known as USS-UPI, LLC, from its joint venture partner for $3 million, net of cash received of $2 million. There was an assumption of accounts payable owed to U. S. Steel for prior sales of steel substrate of $135 million associated with the purchase that is reflected as a reduction in receivables from related parties on the Company's Condensed Consolidated Balance Sheet. Using step acquisition accounting the Company increased the value of its previously held equity investment to its fair value of $5 million which resulted in a gain of approximately $25 million. The gain was recorded in gain on equity investee transactions in the Condensed Consolidated Statement of Operations. Receivables of $44 million, inventories of $96 million, accounts payable and accrued liabilities of $19 million, current portion of long-term debt of $55 million and payroll and employee benefits liabilities of $78 million were recorded with the acquisition. Property, plant and equipment of $97 million which included a fair value step-up of $47 million and an intangible asset of $54 million were also recorded on the Company's Condensed Consolidated Balance Sheet. The intangible asset, which will be amortized over ten years, arises from a land lease contract, under which a certain portion of payment owed to UPI is realized in the form of deductions from electricity costs.

Revenue

Revenue	9 Months Ended
	Sep. 30, 2021
Revenue from Contract with Customer [Abstract]
Revenue	6. Revenue Revenue is generated primarily from contracts to produce, ship and deliver steel products, and to a lesser extent, raw materials sales such as iron ore pellets and coke by-products and real estate sales. Generally, U. S. Steel’s performance obligations are satisfied and revenue is recognized when title transfers to our customer for product shipped or services are provided. Revenues are recorded net of any sales incentives. Shipping and other transportation costs charged to customers are treated as fulfillment activities and are recorded in both revenue and cost of sales at the time control is transferred to the customer. Costs related to obtaining sales contracts are incidental and are expensed when incurred. Because customers are invoiced at the time title transfers and U. S. Steel’s right to consideration is unconditional at that time, U. S. Steel does not maintain contract asset balances. Additionally, U. S. Steel does not maintain contract liability balances, as performance obligations are satisfied prior to customer payment for product. U. S. Steel offers industry standard payment terms. The following tables disaggregate our revenue by product for each of the reportable business segments for the three months and nine months ended September 30, 2021 and 2020, respectively: Net Sales by Product (In millions): Three Months Ended September 30, 2021 Flat-Rolled Mini Mill USSE Tubular Other Total Semi-finished $ — $ — $ 35 $ — $ — $ 35 Hot-rolled sheets 887 571 657 — — 2,115 Cold-rolled sheets 1,037 159 145 — — 1,341 Coated sheets 1,216 219 356 — — 1,791 Tubular products — — 21 217 — 238 All Other (a) 401 — 32 (1) 12 444 Total $ 3,541 $ 949 $ 1,246 $ 216 $ 12 $ 5,964 (a) Consists primarily of sales of raw materials and coke making by-products. Three Months Ended September 30, 2020 Flat-Rolled USSE Tubular Other Total Semi-finished $ 5 $ — $ — $ — $ 5 Hot-rolled sheets 239 193 — — 432 Cold-rolled sheets 555 43 — — 598 Coated sheets 778 233 — — 1,011 Tubular products — 11 91 — 102 All Other (a) 151 15 5 21 192 Total $ 1,728 $ 495 $ 96 $ 21 $ 2,340 (a) Consists primarily of sales of raw materials and coke making by-products. Nine Months Ended September 30, 2021 Flat-Rolled Mini Mill USSE Tubular Other Total Semi-finished $ 12 $ — $ 84 $ — $ — $ 96 Hot-rolled sheets 1,990 1,271 1,604 — — 4,865 Cold-rolled sheets 2,710 365 330 — — 3,405 Coated sheets 3,114 519 988 — — 4,621 Tubular products — — 45 523 — 568 All Other (a) 978 3 71 11 35 1,098 Total $ 8,804 $ 2,158 $ 3,122 $ 534 $ 35 $ 14,653 (a) Consists primarily of sales of raw materials and coke making by-products. Nine Months Ended September 30, 2020 Flat-Rolled USSE Tubular Other Total Semi-finished $ 63 $ 2 $ — $ — $ 65 Hot-rolled sheets 980 544 — — 1,524 Cold-rolled sheets 1,495 114 — — 1,609 Coated sheets 2,202 664 — — 2,866 Tubular products — 31 520 — 551 All Other (a) 459 48 13 44 564 Total $ 5,199 $ 1,403 $ 533 $ 44 $ 7,179 (a) Consists primarily of sales of raw materials and coke making by-products.

Cash, Cash Equivalents and Rest

Cash, Cash Equivalents and Restricted Cash	9 Months Ended
	Sep. 30, 2021
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash, Cash Equivalents and Restricted Cash	7. Cash, Cash Equivalents and Restricted Cash The following table provides a reconciliation of cash, cash equivalents and restricted cash reported within U. S. Steel's Condensed Consolidated Balance Sheets that sum to the total of the same amounts shown in the Condensed Consolidated Statement of Cash Flows: (In millions) September 30, 2021 September 30, 2020 Cash and cash equivalents $ 2,044 $ 1,696 Restricted cash in other current assets 17 2 Restricted cash in other noncurrent assets 91 89 Total cash, cash equivalents and restricted cash $ 2,152 $ 1,787 Amounts included in restricted cash represent cash balances which are legally or contractually restricted, primarily for electric arc furnace construction, environmental and other capital projects, collateral for open cash flow hedge positions and insurance purposes.

Inventories

Inventories	9 Months Ended
	Sep. 30, 2021
Inventory Disclosure [Abstract]
Inventories	8. Inventories The LIFO method is the predominant method of inventory costing for our Flat-Rolled and Tubular segments. The FIFO and moving average methods are the predominant inventory costing methods for our Mini Mill segment and the FIFO method is the predominant inventory costing method for our USSE segment. At September 30, 2021 and December 31, 2020, the LIFO method accounted for 44 percent and 59 percent of total inventory values, respectively. (In millions) September 30, 2021 December 31, 2020 Raw materials $ 631 $ 416 Semi-finished products 1,055 633 Finished products 345 300 Supplies and sundry items 55 53 Total $ 2,086 $ 1,402 Current acquisition costs were estimated to exceed the above inventory values by $1.012 billion and $848 million at September 30, 2021 and December 31, 2020, respectively. As a result of the liquidation of LIFO inventories, cost of sales decreased and earnings before interest and income taxes increased by $5 million and $12 million for the three months and nine months ended September 30, 2021, respectively. Cost of sales decreased and earnings before interest and income taxes increased by $11 million and $5 million for the three months and nine months ended September 30, 2020, respectively, as a result of liquidation of LIFO inventories.

Intangible Assets

Intangible Assets	9 Months Ended
	Sep. 30, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible Assets	9. Intangible Assets and Goodwill Intangible assets that are being amortized on a straight-line basis over their estimated useful lives are detailed below: As of September 30, 2021 As of December 31, 2020 (In millions) Useful Gross Accumulated Net Gross Accumulated Impairment Accumulated Net Customer relationships 22 Years $ 413 $ 13 $ 400 $ 132 $ 55 $ 77 $ — Patents 5-15 Years 17 10 7 22 7 10 5 Energy Contract 10 Years 54 9 45 54 — 5 49 Other 4-15 Years — — — 14 5 9 — Total amortizable intangible assets $ 484 $ 32 $ 452 $ 222 $ 67 $ 101 $ 54 Total estimated amortization expense for the remainder of 2021 is $6 million. We expect approximately $125 million in annual amortization expense through 2026 and approximately $320 million in remaining amortization expense thereafter. The carrying amount of acquired water rights with indefinite lives as of September 30, 2021 and December 31, 2020 totaled $75 million. Below is a summary of goodwill by segment for the nine months ended September 30, 2021: Flat-Rolled Mini Mill USSE Tubular Total Balance at December 31, 2020 $ — $ — $ 4 $ — $ 4 Additions — 905 — — 905 Balance at September 30, 2021 $ — $ 905 $ 4 $ — $ 909

Pensions and Other Benefits

Pensions and Other Benefits	9 Months Ended
	Sep. 30, 2021
Retirement Benefits [Abstract]
Pensions and Other Benefits	10. Pensions and Other Benefits The following table reflects the components of net periodic benefit cost (income) for the three months ended September 30, 2021 and 2020: Pension Benefits Other Benefits (In millions) 2021 2020 2021 2020 Service cost $ 12 $ 13 $ 3 $ 3 Interest cost 41 49 13 16 Expected return on plan assets (91) (84) (21) (20) Amortization of prior service credit — — (7) (1) Amortization of actuarial net loss (gain) 29 36 (6) (4) Net periodic benefit cost (income), excluding below (9) 14 (18) (6) Multiemployer plans 19 19 — — Settlement, termination and curtailment losses (a) 5 2 — — Net periodic benefit cost (income) $ 15 $ 35 $ (18) $ (6) (a) During the three months ended September 30, 2021 and 2020, pension benefits incurred settlement charges of approximately $5 million and $2 million, respectively, due to lump sum payments to certain individuals. The following table reflects the components of net periodic benefit cost (income) for the nine months ended September 30, 2021 and 2020: Pension Benefits Other Benefits (In millions) 2021 2020 2021 2020 Service cost $ 40 $ 38 $ 9 $ 9 Interest cost 122 145 37 48 Expected return on plan assets (269) (249) (61) (60) Amortization of prior service cost 1 1 (21) (5) Amortization of actuarial net loss (gain) 104 108 (18) (12) Net periodic benefit cost (income), excluding below (2) 43 (54) (20) Multiemployer plans 56 58 — — Settlement, termination and curtailment losses (a) 8 10 — — Net periodic benefit cost (income) $ 62 $ 111 $ (54) $ (20) (a) During the nine months ended September 30, 2021, the pension plan incurred settlement and curtailment charges of approximately $8 million due to lump sum payments to certain individuals and the sale of Transtar. For the nine months ended September 30, 2020 the pension plan incurred settlement and special termination charges of approximately $10 million due to workforce restructuring and lump sum payments made to certain individuals. Employer Contributions During the first nine months of 2021, U. S. Steel made cash payments of $56 million to the Steelworkers Pension Trust and $10 million of pension payments not funded by trusts. During the first nine months of 2021, cash payments of $31 million were made for other postretirement benefit payments not funded by trusts. Company contributions to defined contribution plans totaled $11 million and $1 million for the three months ended September 30, 2021 and 2020, respectively. Company contributions to defined contribution plans totaled $32 million and $16 million for the nine months ended September 30, 2021 and 2020, respectively. Transtar Disposition

Stock-Based Compensation Plans

Stock-Based Compensation Plans	9 Months Ended
	Sep. 30, 2021
Share-based Payment Arrangement [Abstract]
Stock-Based Compensation Plans	11. Stock-Based Compensation Plans U. S. Steel has outstanding stock-based compensation awards that were granted by the Compensation & Organization Committee of the Board of Directors, or its designee, under the 2005 Stock Incentive Plan (2005 Plan) and the 2016 Omnibus Incentive Compensation Plan, as amended and restated (Omnibus Plan). The Company's stockholders approved the Omnibus Plan and authorized the Company to issue up to 32,700,000 shares of U. S. Steel common stock under the Omnibus Plan. While the awards that were previously granted under the 2005 Plan remain outstanding, all future awards will be granted under the Omnibus Plan. As of September 30, 2021, there were 15,966,607 shares available for future grants under the Omnibus Plan. Recent grants of stock-based compensation consist of restricted stock units, total stockholder return (TSR) performance awards and return on capital employed (ROCE) performance awards. Shares of common stock under the Omnibus Plan are issued from authorized, but unissued stock. The following table is a summary of the awards made under the Omnibus Plan during the first nine months of 2021 and 2020. 2021 2020 Grant Details Shares (a) Fair Value (b) Shares (a) Fair Value (b) Restricted Stock Units 1,831,880 $ 19.65 2,640,690 $ 8.82 Performance Awards (c) TSR 306,930 $ 19.46 671,390 $ 8.19 ROCE (d) 485,900 $ 17.92 — $ — (a) The share amounts shown in this table do not reflect an adjustment for estimated forfeitures. (b) Represents the per share weighted average for all grants during the period. (c) The number of performance awards shown represents the target share grant of the award. (d) The ROCE awards granted in 2020 and a portion of ROCE awards granted in 2021 are not shown in the table because they were granted in cash. U. S. Steel recognized pretax stock-based compensation expense in the amount of $15 million and $8 million in the three-month periods ended September 30, 2021 and 2020, respectively, and $41 million and $20 million in the first nine months of 2021 and 2020, respectively. As of September 30, 2021, total future compensation expense related to nonvested stock-based compensation arrangements was $46 million, and the weighted average period over which this expense is expected to be recognized is approximately 16 months. Restricted stock units awarded as part of annual grants generally vest ratably over three years. Their fair value is the market price of the underlying common stock on the date of grant. Restricted stock units granted in connection with new-hire or retention grants generally cliff vest three years from the date of the grant. TSR performance awards may vest at varying levels at the end of a three-year performance period if U. S. Steel's total stockholder return compared to the total stockholder return of a peer group of companies meets specified performance criteria with each year in the three-year performance period weighted at 20 percent and the full three-year performance weighted at 40 percent. TSR performance awards can vest at between zero and 200 percent of the target award. The fair value of the TSR performance awards is calculated using a Monte Carlo simulation. ROCE performance awards may vest at the end of a three-year performance period contingent upon meeting the specified ROCE performance metric. ROCE performance awards can vest between zero and 200 percent of the target award. The fair value of the ROCE performance awards is the average market price of the underlying common stock on the date of grant.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2021
Income Tax Disclosure [Abstract]
Income Taxes	12. Income Taxes Tax provision For the nine months ended September 30, 2021 and 2020, the Company recorded a tax provision of $224 million and a benefit of $48 million, respectively. The tax provisions for the first nine months of 2021 and 2020 were based on an estimated annual effective rate, which requires management to make its best estimate of annual pretax income or loss and discrete items recognized during the period. The tax provision for the nine months ended September 30, 2021 includes a benefit of $514 million for the release of the domestic valuation allowance recorded against domestic deferred tax assets that are more likely than not to be realized. During the third quarter of 2021, the Company evaluated all available positive and negative evidence, including the impact of profitability generated from current year operations and future projections of profitability. As a result, the Company determined that, consistent with the prior quarter, all of its domestic deferred tax assets were more likely than not to be realized with the exception of certain of its state net operating losses and state tax credits and reversed the valuation allowance against those deferred tax assets accordingly. The tax benefit for the nine months ended September 30, 2020 includes a $39 million benefit related to recording a loss from continuing operations and income from other comprehensive income categories and expense of $13 million for an updated estimate to tax reserves related to an unrecognized tax benefit. Due to the full valuation allowance on our domestic deferred tax assets, the tax benefit in 2020 does not reflect any additional tax benefit for domestic pretax losses. Throughout the year, management regularly updates forecasted annual pretax results for the various countries in which we operate based on changes in factors such as prices, shipments, product mix, plant operating performance and cost estimates. To the extent that actual 2021 pretax results for U.S. and foreign income or loss vary from estimates applied herein, the actual tax provision or benefit recognized in 2021 could be materially different from the forecasted amount used to estimate the tax provision for the nine months ended September 30, 2021.

Earnings and Dividends Per Comm

Earnings and Dividends Per Common Share	9 Months Ended
	Sep. 30, 2021
Earnings Per Share [Abstract]
Earnings and Dividends Per Common Share	13. Earnings and Dividends Per Common Share Earnings (Loss) Per Share Attributable to United States Steel Corporation Stockholders The effect of dilutive securities on weighted average common shares outstanding included in the calculation of diluted earnings (loss) per common share for the three and nine months ended September 30, 2021 and September 30, 2020 were as follows. Three Months Ended September 30, Nine Months Ended September 30, (Dollars in millions, except per share amounts) 2021 2020 2021 2020 Earnings (loss) attributable to United States Steel Corporation stockholders $ 2,002 $ (234) $ 3,105 $ (1,214) Weighted-average shares outstanding (in thousands): Basic 270,175 220,402 263,209 188,766 Effect of Senior Convertible Notes 12,199 — 11,082 — Effect of stock options, restricted stock units and performance awards 5,089 — 4,812 — Adjusted weighted-average shares outstanding, diluted 287,463 220,402 279,103 188,766 Basic earnings (loss) per common share $ 7.41 $ (1.06) $ 11.80 $ (6.43) Diluted earnings (loss) per common share $ 6.97 $ (1.06) $ 11.13 $ (6.43) Excluded from the computation of diluted earnings (loss) per common share due to their anti-dilutive effect were 0.6 million and 1.2 million outstanding securities granted under the Omnibus Plan for the three and nine months ended September 30, 2021, respectively, and 5.7 million and 5.5 million outstanding securities granted under the Omnibus Plan for the three and nine months ended September 30, 2020, respectively. Dividends Paid Per Share The dividend for each of the first, second and third quarters of 2021 and 2020 was one cent per common share.

Derivative Instruments

Derivative Instruments	9 Months Ended
	Sep. 30, 2021
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments	14. Derivative Instruments The USSE segment uses foreign exchange forward sales contracts (foreign exchange forwards) to exchange euros for U.S. dollars (USD), our Flat-Rolled segment used foreign exchange forwards to exchange USD for Canadian dollars and our Mini Mill segment uses foreign exchange forwards to exchange USD for euros. All of our foreign exchange forwards have maturities no longer than 13 months and are used to mitigate the risk of foreign currency exchange rate fluctuations and manage our foreign currency requirements. The USSE and Flat-Rolled segments use hedge accounting for their foreign exchange forwards. The Mini Mill segment has not elected hedge accounting; therefore, the changes in the fair value of their foreign exchange forwards are recognized immediately in the Condensed Consolidated Statements of Operations (mark-to-market accounting). The Flat-Rolled and USSE segments also use financial swaps to protect from the commodity price risk associated with purchases of natural gas, zinc, tin and electricity (commodity purchase swaps). We elected cash flow hedge accounting for Flat-Rolled commodity purchase swaps for natural gas, zinc and tin and use mark-to-market accounting for electricity swaps used in our domestic operations and for commodity purchase swaps used in our European operations. The maximum derivative contract duration for commodity purchase swaps where hedge accounting was elected and was not elected is 15 months and 27 months, respectively. The Flat-Rolled and Mini Mill segments have entered into financial swaps that are used to partially manage the sales price risk of certain hot-rolled coil sales (sales swaps). The Flat-Rolled segment uses hedge accounting for its sales swaps and the Mini Mill segment uses mark-to-market accounting for its sales swaps. Sales swaps have maturities of up to three months. The table below shows the outstanding swap quantities used to hedge forecasted purchases and sales as of September 30, 2021 and September 30, 2020: Hedge Contracts Classification September 30, 2021 September 30, 2020 Natural gas (in mmbtus) Commodity purchase swaps 38,661,000 34,222,000 Tin (in metric tons) Commodity purchase swaps 1,384 787 Zinc (in metric tons) Commodity purchase swaps 12,853 8,148 Electricity (in megawatt hours) Commodity purchase swaps 909,240 847,680 Hot-rolled coils (in tons) Sales swaps 97,320 — Foreign currency (in millions of euros) Foreign exchange forwards € 290 € 240 Foreign currency (in millions of dollars) Foreign exchange forwards $ 9 $ — Foreign currency (in millions of CAD) Foreign exchange forwards $ — $ 8 There were $68 million and $5 million in accounts receivable and $103 million and $54 million in accounts payable recorded for derivatives designated as hedging instruments as of September 30, 2021 and December 31, 2020, respectively. Amounts recorded in long-term asset and long-term liability accounts for derivatives were not material as of September 30, 2021 and December 31, 2020. Accounts receivable and accounts payable recorded in the Condensed Consolidated Balance sheet for derivatives not designated as hedging instruments were $13 million and $2 million as of September 30, 2021, respectively, and were both immaterial as of December 31, 2020. The table below summarizes the effect of hedge accounting on Accumulated Other Comprehensive Income (AOCI) and amounts reclassified from AOCI into earnings for the three and nine months ended September 30, 2021 and 2020: Gain (Loss) on Derivatives in AOCI Amount of Gain (Loss) Recognized in Income (In millions) Three Months Ended September 30, 2021 Three Months Ended September 30, 2020 Location of Reclassification from AOCI (a) Three Months Ended September 30, 2021 Three Months Ended September 30, 2020 Sales swaps $ 52 $ — Net sales $ (60) $ — Commodity purchase swaps 20 19 Cost of sales (b) 14 (6) Foreign exchange forwards 8 (9) Cost of sales 1 (3) (a) The earnings impact of our hedging instruments substantially offsets the earnings impact of the related hedged items resulting in immaterial ineffectiveness. (b) Costs for commodity purchase swaps are recognized in cost of sales as products are sold. Gain (Loss) on Derivatives in AOCI Amount of Gain (Loss) Recognized in Income (In millions) Nine Months Ended September 30, 2021 Nine Months Ended September 30, 2020 Location of Reclassification from AOCI (a) Nine Months Ended September 30, 2021 Nine Months Ended September 30, 2020 Sales swaps $ (71) $ — Net sales $ (93) $ — Commodity purchase swaps 52 30 Cost of sales (b) 18 (26) Foreign exchange forwards 29 (8) Cost of sales (9) (2) (a) The earnings impact of our hedging instruments substantially offsets the earnings impact of the related hedged items resulting in immaterial ineffectiveness. (b) Costs for commodity purchase swaps are recognized in cost of sales as products are sold. At current contract values, $62 million currently in AOCI as of September 30, 2021 will be recognized as a decrease in cost of sales over the next year and $97 million currently in AOCI as of September 30, 2021 will be recognized as a decrease in net sales over the next year.

Debt

Debt	9 Months Ended
	Sep. 30, 2021
Debt Disclosure [Abstract]
Debt	15. Debt (In millions) Issuer/Borrower Interest Maturity September 30, 2021 December 31, 2020 2037 Senior Notes U. S. Steel 6.650 2037 350 350 2029 Senior Secured Notes Big River Steel 6.625 2029 720 — 2029 Senior Notes U. S. Steel 6.875 2029 750 — 2026 Senior Notes U. S. Steel 6.250 2026 230 650 2026 Senior Convertible Notes U. S. Steel 5.000 2026 350 350 2025 Senior Notes U. S. Steel 6.875 2025 — 750 2025 Senior Secured Notes U. S. Steel 12.000 2025 — 1,056 Arkansas Teacher Retirement System Notes Payable Big River Steel 5.500 - 7.750 2023 106 — Export-Import Credit Agreement U. S. Steel Variable 2021 — 180 Environmental Revenue Bonds U. S. Steel 4.125 - 6.750 2024 - 2050 717 717 Environmental Revenue Bonds Big River Steel 4.500 - 4.750 2049 752 — Finance leases and all other obligations U. S. Steel Various 2021 - 2029 78 81 Finance leases and all other obligations Big River Steel Various 2021 - 2031 153 — Export Credit Agreement (ECA) U. S. Steel Variable 2031 136 113 Credit Facility Agreement U. S. Steel Variable 2024 — 500 Big River Steel ABL Facility Big River Steel Variable 2026 — — USSK Credit Agreement U. S. Steel Kosice Variable 2026 — 368 USSK Credit Facility U. S. Steel Kosice Variable 2021 — — Total Debt 4,342 5,115 Less unamortized discount, premium, and debt issuance costs 9 228 Less short-term debt, long-term debt due within one year, and short-term issuance costs 61 192 Long-term debt $ 4,272 $ 4,695 The following is a summary of debt repayments for our Senior Secured Notes, Senior Notes and Export-Import Credit Agreement made during the nine months ended September 30, 2021: Nine Months Ended September 30, 2021 Debt Instrument (in Millions) Date Debt Extinguished 6.250% Senior Notes due 2026 (a) Third quarter 2021 370 6.875% Senior Notes due 2025 (a) Third quarter 2021 718 6.625% 2029 Senior Secured Notes (a) Third quarter 2021 180 6.250% Senior Notes due 2026 Second quarter 2021 18 6.875% Senior Notes due 2025 Second quarter 2021 14 12.000% 2025 Senior Secured Notes (b) First quarter 2021 1,056 6.875% Senior Notes due 2025 First quarter 2021 18 6.250% Senior Notes due 2026 First quarter 2021 32 Export-Import Credit Agreement (c) First quarter 2021 180 Total $ 2,586 (a) During the three months ended September 30, 2021, there were redemption premiums paid of $28 million and a net gain of $5 million for the write-off of unamortized acquisition-related fair value adjustment, discounts, and debt issuance costs as a result of these debt repayments. (b) There were redemption premiums and unamortized discount and debt issuance write-offs of approximately $181 million and $71 million, respectively related to the repayment. (c) Export-Import Credit Agreement was terminated in the first quarter of 2021. There were approximately $3 million in non-cash debt extinguishment costs associated with the repayment. 2029 Senior Notes On February 11, 2021, U. S. Steel issued $750 million aggregate principal amount of 6.875% Senior Notes due 2029 (2029 Senior Notes). U. S. Steel received net proceeds of approximately $739 million after fees of approximately $11 million related to underwriting and third-party expenses. The net proceeds from the issuance of the 2029 Senior Notes, together with the proceeds of our recent common stock issuance were used to redeem all of our outstanding 2025 Senior Secured Notes. The 2029 Senior Notes will pay interest semi-annually in arrears on March 1 and September 1 of each year beginning on September 1, 2021, and will mature on March 1, 2029, unless earlier redeemed or repurchased. On and after March 1, 2024, the Company may redeem the 2029 Senior Notes at its option, at any time in whole or from time to time in part, upon not less than 15 nor more than 60 days’ notice, at the redemption prices (expressed in percentages of principal amount) listed below, plus accrued and unpaid interest on the 2029 Senior Notes, if any, to, but excluding, the applicable redemption date, if redeemed during the twelve-month period beginning on March 1 of each of the years indicated below. Year Redemption Price 2024 103.438 % 2025 101.719 % 2026 and thereafter 100.000 % At any time prior to March 1, 2024, U. S. Steel may also redeem the 2029 Senior Notes, at our option, in whole or in part, or from time to time, at a price equal to the greater of 100 percent of the principal amount of the 2029 Senior Notes to be redeemed, or the sum of the present value of the redemption price of the 2029 Senior Notes if they were redeemed on March 1, 2024 plus interest payments due through March 1, 2024 discounted to the date of redemption on a semi-annual basis at the applicable treasury yield, plus 50 basis points and accrued and unpaid interest, if any. At any time prior to March 1, 2024 we may also purchase up to 35% of the original aggregate principal amount of the 2029 Senior Notes at 106.875%, plus accrued and unpaid interest, if any, up to, but excluding the applicable date of redemption, with proceeds from equity offerings. Similar to our other senior notes, the indenture governing the 2029 Senior Notes restricts our ability to create certain liens, to enter into sale leaseback transactions and to consolidate, merge, transfer or sell all, or substantially all of our assets. It also contains provisions requiring that U. S. Steel make an offer to purchase the 2029 Senior Notes from holders upon a change of control under certain specified circumstances, as well as other customary provisions. 2029 Senior Secured Notes On September 18, 2020, Big River Steel's indirect subsidiaries, Big River Steel LLC and BRS Finance Corp. (Issuers), issued $900 million in aggregate principal amount of 6.625% Senior Secured Notes (Green Bonds) (2029 Senior Secured Notes). The 2029 Senior Secured Notes pay interest semi-annually in arrears on January 31 and July 31 of each year and will mature on January 31, 2029, unless earlier redeemed or repurchased. On and after September 15, 2023, the Issuers may redeem the 2029 Senior Secured Notes at their option, at any time in whole or from time to time in part, at the redemption prices (expressed in percentages of principal amount) listed below, plus accrued and unpaid interest on the Notes, if any, to, but excluding, the applicable redemption date, if redeemed during the twelve-month period beginning on September 15 of each of the years indicated below. Year Redemption Price 2023 103.313 % 2024 101.656 % 2025 and thereafter 100.000 % At any time prior to September 15, 2023, the Issuers may at their option on one or more occasions redeem up to $90 million of the Notes during each twelve-month period commencing with September 18, 2020 at a redemption price of 103.00% of the principal amount thereof, plus accrued and unpaid interest. The obligations under the 2029 Senior Secured Notes are fully and unconditionally guaranteed, jointly and severally, on a secured basis by the Issuers’ parent company, BRS Intermediate Holdings LLC (BRS Intermediate), which is a direct subsidiary of Big River Steel, and by all future direct and indirect wholly owned domestic subsidiaries of the Issuers. Additionally, the 2029 Senior Secured Notes and related guarantees are secured by (i) first priority liens on most of the tangible and intangible assets of the Issuers and the guarantors and all of the equity interests of the Issuers held by BRS Intermediate (shared in equal priority with each other pari passu lien secured party) (ii) and second priority liens on accounts receivable, inventory and certain other related assets of the Issuers and the guarantors (shared in equal priority with each other pari passu lien secured party). If the Issuers or BRS Intermediate experience specified change in control events, the Issuers must make an offer to purchase the 2029 Senior Secured Notes. If the Issuers sell assets under specified circumstances, the Issuers must make an offer to purchase the 2029 Senior Secured Notes at a price equal to 100% of the aggregate principal amount plus accrued and unpaid interest. The Indenture also limits the ability of the Issuers and their restricted subsidiaries to: incur or guarantee additional indebtedness; pay dividends and make other restricted payments; make investments; consummate certain asset sales; engage in transactions with affiliates; grant or assume liens; and consolidate, merge or transfer all or substantially all of their assets. The Indenture also includes other customary events of default. Big River Steel Environmental Revenue Bonds - Series 2019 On May 31, 2019, Arkansas Development Finance Authority (ADFA) issued $487 million of tax-exempt bonds and loaned 100% of the proceeds to Big River Steel LLC under a bond financing agreement to finance the expansion of Big River Steel's electric arc furnace steel mill and fund the issuance cost of the bonds (2019 ADFA Bonds). The 2019 ADFA Bonds accrue interest at the rate of 4.50% per annum payable semiannually on March 1 and September 1 of each year with a final maturity of September 1, 2049. The 2019 ADFA Bonds are subject to optional redemption during the periods and at the redemption prices shown below plus, in each case, accrued interest. Year Redemption Price September 1, 2026 to August 31, 2027 103 % September 1, 2027 to August 31, 2028 102 % September 1, 2028 to August 31, 2029 101 % On and after September 1, 2029 100 % Prior to September 1, 2026, the 2019 ADFA Bonds are not redeemable. The 2019 ADFA Bonds are fully and unconditionally guaranteed on a senior secured basis, jointly and severally, by BRS Intermediate, BRS Finance Corp. and all future direct and indirect wholly owned domestic subsidiaries of Big River Steel LLC, and secured by first priority liens on most of the tangible and intangible assets and second priority liens on accounts receivable, inventory and certain other related assets of BRS Intermediate. The 2019 ADFA Bonds are subject to certain mandatory sinking fund redemption provisions beginning in 2040, as well as extraordinary mandatory redemption, at a redemption price equal to 100% of the principal amount thereof plus accrued interest to the date fixed for redemption, from surplus funds at the earlier of the completion of the tax-exempt project or expiration of a certain period for construction financings, and upon an event of taxability. The 2019 ADFA Bonds are subject to substantially similar asset sale offer and change of control offer provisions, affirmative and negative covenants, events of default and remedies as the Indenture governing the 2029 Senior Secured Notes. Big River Steel Environmental Revenue Bonds - Series 2020 On September 10, 2020, ADFA issued $265 million of tax-exempt bonds with a green bond designation and loaned 100% of the proceeds to Big River Steel LLC under a bond financing agreement to finance or refinance the expansion of Big River Steel's electric arc furnace steel mill and fund the issuance cost of the bonds (2020 ADFA Bonds). The 2020 ADFA Bonds accrue interest at 4.75% per annum payable semi-annually on March 1 and September 1 of each year with final maturity on September 1, 2049. The 2020 ADFA Bonds are subject to optional redemption during the periods and at the redemption prices shown below, plus, in each case accrued interest. Year Redemption Price September 1, 2027 to August 31, 2028 103 % September 1, 2028 to August 31, 2029 102 % September 1, 2029 to August 31, 2030 101 % On and after September 1, 2030 100 % At any time prior to September 1, 2027, Big River Steel LLC may also redeem the 2020 ADFA Bonds, at its option, in whole or in part, or from time to time, at a price equal to the greater of 100 percent of the principal amount of the 2020 ADFA Bonds to be redeemed, or the present value of the redemption price of the 2020 ADFA Bonds if they were redeemed on September 1, 2027 plus interest payments due through September 1, 2027 discounted to the date of redemption on a semi-annual basis at the applicable tax exempt municipal bond rate and accrued and unpaid interest to the date fixed for redemption. The 2020 ADFA Bonds are fully and unconditionally guaranteed, jointly and severally, on a secured basis by certain of Big River Steel's subsidiaries and subject to first priority liens and second priority liens on certain Big River Steel collateral. The 2020 ADFA Bonds are subject to substantially similar asset sale offer and change of control offer provisions, affirmative and negative covenants, events of default and remedies as the Indenture governing the 2029 Senior Secured Notes. Arkansas Teacher Retirement System Notes Payable Big River Steel entered into three financing agreements with the Arkansas Teacher Retirement System during 2018 and 2019. The interest rates on the notes range from 5.50% to 7.75% at present. Interest on these agreements may be paid-in-kind through the respective dates of maturity and therefore requires no interim debt service by Big River Steel prior to the date of maturity or early repayment, as the case may be. One such agreement has the benefit of a pledge of future income streams generated through an anticipated monetization of recycling tax credits provided by the State of Arkansas in conjunction with the expansion of Big River Steel. As of September 30, 2021, the outstanding balance for these financing agreements was $106 million. Big River Steel may prepay amounts owed under these agreements at any time without penalty. On October 21, 2021, Big River Steel repaid two of the financing agreements in the aggregate principal amount of approximately $20 million. Big River Steel - Sustainability Linked ABL Facility On July 23, 2021, Big River Steel entered into an amendment to its senior secured asset-based revolving credit facility (Big River Steel ABL Facility), which extended the maturity by 5 years and added sustainability targets related to carbon reduction, safety performance and facility certification by ResponsibleSteel™. The Big River Steel ABL Facility is secured by first-priority liens on accounts receivable and inventory and certain other assets and second priority liens on most tangible and intangible assets of Big River Steel in each case subject to permitted liens. The Big River Steel ABL Facility provides for borrowings for working capital and general corporate purposes in an amount equal up to the lesser of (a) $350 million and (b) a borrowing base calculated based on specified percentages of eligible accounts receivables and inventory, subject to certain adjustments and reserves. The Big River Steel ABL Facility matures on July 23, 2026. The outstanding principal balance was zero at September 30, 2021. Availability under the Big River Steel ABL Facility, pursuant to the available borrowing base was $350 million at September 30, 2021. The Big River Steel ABL Facility provides for borrowings at interest rates based on defined, short-term market rates plus a spread based on availability. The Big River Steel ABL Facility also requires a commitment fee on the unused portion of the Big River Steel ABL Facility, determined quarterly based on Big River Steel LLC's utilization levels. Big River Steel LLC must maintain a fixed charge coverage ratio of at least 1.00 to 1.00 for the most recent twelve consecutive months when availability under the Big River Steel ABL Facility is less than the greater of ten percent of the borrowing base availability and $13 million. Based on the most recent four quarters as of September 30, 2021, Big River Steel would have met the fixed charge coverage ratio test. The Big River Steel ABL Facility includes affirmative and negative covenants that are customary for facilities of this type. The Big River Steel ABL Facility also includes customary events of default. U. S. Steel - Sustainability Linked Credit Facility Agreement The Fifth Amended and Restated Credit Facility Agreement (Credit Facility Agreement) was amended on July 23, 2021 to include targets related to carbon reduction, safety performance and facility certification by ResponsibleSteel™. In addition to the new sustainability link, the Credit Facility Agreement was amended to reduce the facility size to $1.75 billion from $2 billion, which supports the Company’s current footprint and is consistent with the its efforts to optimize its global liquidity position. As of September 30, 2021, there were approximately $4 million of letters of credit issued, and no loans drawn under the Credit Facility Agreement. The availability under the Credit Facility Agreement was $1.746 billion as of September 30, 2021. U. S. Steel must maintain a fixed charge coverage ratio of at least 1.00 to 1.00 for the most recent four consecutive quarters when availability under the Credit Facility Agreement is less than the greater of ten percent of the total aggregate commitments and $175 million. Based on the most recent four quarters as of September 30, 2021, the Company would have met the fixed charge coverage ratio test. U. S. Steel Košice ( USSK) Credit Facilities On September 29, 2021, USSK entered into a €300 million (approximately $347 million) unsecured sustainability linked credit agreement (USSK Credit Agreement), replacing the previous €460 million credit facility agreement. The USSK Credit Agreement matures in 5 years and contains sustainability targets related to carbon reduction, safety performance and facility certification by ResponsibleSteel™. At September 30, 2021, USSK had no borrowings under the USSK Credit Agreement.

Fair Value of Financial Instrum

Fair Value of Financial Instruments	9 Months Ended
	Sep. 30, 2021
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	16. Fair Value of Financial Instruments The carrying value of cash and cash equivalents, current accounts and notes receivable, accounts payable, bank checks outstanding, and accrued interest included in the Condensed Consolidated Balance Sheet approximate fair value. See Note 14 for disclosure of U. S. Steel’s derivative instruments, which are accounted for at fair value on a recurring basis. Big River Steel On October 31, 2019, a wholly owned subsidiary of U. S. Steel purchased a 49.9% ownership interest in Big River Steel. The transaction included a call option (U. S. Steel Call Option) to acquire the remaining equity interest within the next four years at an agreed-upon price formula. The investment purchase included other options that were marked to fair value during 2020. The net change in fair value of the options during the nine months ended September 30, 2020 resulted in a $40 million decrease to other financial costs. When the U. S. Steel Call Option was exercised on December 8, 2020, the other options were legally extinguished and a new contingent forward asset was recorded for $11 million. As the contingent forward was a contract to purchase a business, it was no longer considered a derivative subject to ASC 815, Derivative Instruments and Hedging Activities , and was not subject to subsequent fair value adjustments. The contingent forward asset was removed with the recognition of the gain on the previously held investment in Big River Steel when the purchase of the remaining interest closed on January 15, 2021. See Note 20 to the Consolidated Financial Statements in our Annual Report on Form 10-K for the year-ended December 31, 2020 and Note 5 for further details. Prior to exercise of the U. S. Steel Call Option, the options were marked to fair value each period using a Monte Carlo simulation which is considered a Level 3 valuation technique. Level 3 valuation techniques include inputs to the valuation methodology that are considered unobservable and significant to the fair value measurement. The simulation relied on assumptions that included Big River Steel's equity value, volatility, the risk-free interest rate and U. S. Steel's credit spread. Stelco Option for Minntac Mine Interest On April 30, 2020 (Effective Date), the Company entered into an Option Agreement with Stelco, Inc. (Stelco), that grants Stelco the option to purchase a 25 percent interest (Option Interest) in a to-be-formed entity (Joint Venture) that will own the Company’s current iron ore mine located in Mt. Iron, Minnesota (Minntac Mine). As consideration for the Option, Stelco paid the Company an aggregate amount of $100 million in five $20 million installments, which began on the Effective Date and ended on December 31, 2020 and are recorded net of transaction costs in noncontrolling interest in the Condensed Consolidated Balance Sheet. In the event Stelco exercises the option, Stelco will contribute an additional $500 million to the Joint Venture, which amount shall be remitted solely to U. S. Steel in the form of a one-time special distribution, and the parties will engage in good faith negotiations to finalize the master agreement (pursuant to which Stelco will acquire the Option Interest) and the limited liability company agreement of the Joint Venture. The following table summarizes U. S. Steel’s financial liabilities that were not carried at fair value at September 30, 2021 and December 31, 2020. The fair value of long-term debt was determined using Level 2 inputs. September 30, 2021 December 31, 2020 (In millions) Fair Carrying Fair Carrying Financial liabilities: Short-term and long-term debt (a) $ 4,663 $ 3,996 $ 5,323 $ 4,806 (a) Excludes finance lease obligations.

Statement of Changes in Stockho

Statement of Changes in Stockholders' Equity	9 Months Ended
	Sep. 30, 2021
Equity [Abstract]
Statement of Changes in Stockholders' Equity	17. Statement of Changes in Stockholders’ Equity The following table reflects the first nine months of 2021 and 2020 reconciliation of the carrying amount of total equity, equity attributable to U. S. Steel and equity attributable to noncontrolling interests: Nine Months Ended September 30, 2021 (In millions) Total (Accumulated Deficit) Retained Earnings Accumulated Common Treasury Paid-in Non- Balance at beginning of year $ 3,879 $ (623) $ (47) $ 229 $ (175) $ 4,402 $ 93 Comprehensive income (loss): Net earnings 91 91 — — — — — Other comprehensive income (loss), net of tax: Pension and other benefit adjustments 24 — 24 — — — — Currency translation adjustment (47) — (47) — — — — Derivative financial instruments (20) — (20) — — — — Employee stock plans 6 — — 2 (7) 11 — Common Stock Issued 790 — — 48 — 742 — Dividends paid on common stock (3) — — — — (3) — Balance at March 31, 2021 $ 4,720 $ (532) $ (90) $ 279 $ (182) $ 5,152 $ 93 Comprehensive income (loss): Net earnings 1,012 1,012 — — — — — Other comprehensive income (loss), net of tax: Pension and other benefit adjustments 205 — 205 — — — — Currency translation adjustment 23 — 23 — — — — Derivative financial instruments (31) — (31) — — — — Employee stock plans 17 — — — (1) 18 — Dividends paid on common stock (2) — — — — (2) — Other (1) — — — — — (1) Balance at June 30, 2021 $ 5,943 $ 480 $ 107 $ 279 $ (183) $ 5,168 $ 92 Comprehensive income (loss): Net earnings 2,002 2,002 — — — — — Other comprehensive income (loss), net of tax: Pension and other benefit adjustments 15 — 15 — — — — Currency translation adjustment (26) — (26) — — — — Derivative financial instruments 60 — 60 — — — — Employee stock plans 16 — — (1) 17 — Dividends paid on common stock (3) (3) — — — — — Other 1 1 — — — — — Balance at September 30, 2021 $ 8,008 $ 2,480 $ 156 $ 279 $ (184) $ 5,185 $ 92 Nine Months Ended September 30, 2020 (In millions) Total Retained Earnings (Accumulated Deficit) Accumulated Common Treasury Paid-in Non- Balance at beginning of year $ 4,093 $ 544 $ (478) $ 179 $ (173) $ 4,020 $ 1 Comprehensive income (loss): Net loss (391) (391) — — — — — Other comprehensive income (loss), net of tax: Pension and other benefit adjustments 52 — 52 — — — — Currency translation adjustment (23) — (23) — — — — Derivative financial instruments (5) — (5) — — — — Employee stock plans 2 — — — (2) 4 — Dividends paid on common stock (2) (2) — — — — — Balance at March 31, 2020 $ 3,726 $ 151 $ (454) $ 179 $ (175) $ 4,024 $ 1 Comprehensive income (loss): Net loss (589) (589) — — — — — Other comprehensive income (loss), net of tax: Pension and other benefit adjustments 29 — 29 — — — — Currency translation adjustment 20 — 20 — — — — Derivative financial instruments 15 — 15 — — — — Employee stock plans 8 — — — — 8 — Common Stock Issued 410 — — 50 — 360 — Dividends paid on common stock (1) — — — — (1) — Stelco Option Agreement 37 — — — — — 37 Other (1) — — — — — (1) Balance at June 30, 2020 $ 3,654 $ (438) $ (390) $ 229 $ (175) $ 4,391 $ 37 Comprehensive income (loss): Net loss (234) (234) — — — — — Other comprehensive income (loss), net of tax: Pension and other benefit adjustments 16 — 16 — — — — Currency translation adjustment 34 — 34 — — — — Derivative financial instruments 8 — 8 — — — — Employee stock plans 10 — — — — 10 — Dividends paid on common stock (3) — — — — (3) — Stelco Option Agreement 18 — — — — — 18 Other 1 1 — — — — — Balance at September 30, 2020 $ 3,504 $ (671) $ (332) $ 229 $ (175) $ 4,398 $ 55

Reclassifications from Accumula

Reclassifications from Accumulated Other Comprehensive Income (AOCI)	9 Months Ended
	Sep. 30, 2021
Equity [Abstract]
Reclassifications from Accumulated Other Comprehensive Income (AOCI)	18. Reclassifications from Accumulated Other Comprehensive Income (AOCI) (In millions) Pension and Foreign Unrealized (Loss) Gain on Derivatives Total Balance at December 31, 2020 $ (458) $ 449 $ (38) $ (47) Other comprehensive income (loss) before reclassifications 190 (50) (49) 91 Amounts reclassified from AOCI (a) 54 — 58 112 Net current-period other comprehensive income (loss) 244 (50) 9 203 Balance at September 30, 2021 $ (214) $ 399 $ (29) $ 156 Balance at December 31, 2019 $ (843) $ 381 $ (16) $ (478) Other comprehensive income (loss) before reclassifications 6 31 (6) 31 Amounts reclassified from AOCI (a) 91 — 24 115 Net current-period other comprehensive income 97 31 18 146 Balance at September 30, 2020 $ (746) $ 412 $ 2 $ (332) (a) See table below for further details. Amount reclassified from AOCI (a) Three Months Ended September 30, Nine Months Ended September 30, Details about AOCI components (in millions) 2021 2020 2021 2020 Amortization of pension and other benefit items Prior service credits (a) $ (7) $ (1) $ (20) $ (4) Actuarial losses (a) 23 32 86 96 Settlement, termination and curtailment losses (a) 5 2 6 2 UPI Purchase Accounting Adjustment — — — 23 Total pensions and other benefits items 21 33 72 117 Derivative reclassifications to Condensed Consolidated Statements of Operations 40 6 77 28 Total before tax 61 39 149 145 Tax provision (15) (15) (37) (30) Net of tax $ 46 $ 24 $ 112 $ 115 (a) These AOCI components are included in the computation of net periodic benefit cost. See Note 10 for additional details.

Transactions with Related Parti

Transactions with Related Parties	9 Months Ended
	Sep. 30, 2021
Related Party Transactions [Abstract]
Transactions with Related Parties	19. Transactions with Related Parties Related party sales and service transactions are primarily related to equity investees and were $341 million and $268 million for the three months ended September 30, 2021 and 2020, respectively, and $977 million and $710 million for the nine months ended September 30, 2021 and 2020, respectively. Accounts payable to related parties include balances due to PRO-TEC Coating Company, LLC (PRO-TEC) of $128 million and $86 million at September 30, 2021 and December 31, 2020, respectively for invoicing and receivables collection services provided by U. S. Steel on PRO-TEC's behalf. U. S. Steel, as PRO-TEC’s exclusive sales agent, is responsible for credit risk related to those receivables. U. S. Steel also provides PRO-TEC marketing, selling and customer service functions. Payables to other related parties totaled $2 million and $19 million for the periods ending September 30, 2021 and December 31, 2020, respectively. Purchases from related parties for outside processing services provided by equity investees amounted to $6 million and $9 million for the three months ended September 30, 2021 and 2020, respectively, and $32 million and $47 million for the nine months ended September 30, 2021 and 2020, respectively. Purchases of iron ore pellets from related parties amounted to $26 million and $19 million for the three months ended September 30, 2021 and 2020, respectively, and $80 million and $53 million for the nine months ended September 30, 2021 and 2020, respectively.

Restructuring and Other Charges

Restructuring and Other Charges	9 Months Ended
	Sep. 30, 2020
Restructuring and Related Activities [Abstract]
Restructuring and Other Charges	20. Restructuring and Other Charges During the three months ended September 30, 2021, the Company did not record any restructuring and other charges. Cash payments were made related to severance and exit costs of approximately $9 million. During the nine months ended September 30, 2021, the Company recorded restructuring and other charges of $37 million, which consists of $27 million for Great Lakes Works and $10 million for environmental related charges at other facilities and costs related to severance. Cash payments were made related to severance and exit costs of approximately $53 million. During the nine months ended September 30, 2020, the Company recorded restructuring and other charges of $130 million, which consists of charges of $72 million for the indefinite idling of our Keetac mining operations and a significant portion of Great Lakes Works, $13 million for the indefinite idling of Lorain Tubular Operations and Lone Star Tubular Operations, and $13 million and $32 million for employee benefit costs related to Company-wide headcount reductions and headcount reductions under a Voluntary Early Retirement Program offered at USSK, respectively. Cash payments were made related to severance and exit costs of approximately $130 million. Approximately $29 million of these cash payments were funded by the postretirement benefit trust (VEBA) per an agreement with the United Steelworkers of America. The activity in the accrued balances incurred in relation to restructuring programs during the nine months ended September 30, 2021 were as follows: (In millions) Employee Related Costs Exit Costs Non-cash Charges Total Balance at December 31, 2020 $ 51 $ 126 $ — $ 177 Additional charges 3 33 1 37 Cash payments/utilization (a) (35) (26) (1) (62) Balance at September 30, 2021 $ 19 $ 133 $ — $ 152 (a) Payments of $8 million were made from the pension fund trust. Accrued liabilities for restructuring programs are included in the following balance sheet lines: (In millions) September 30, 2021 December 31, 2020 Accounts payable $ 35 $ 34 Payroll and benefits payable 6 29 Employee benefits 13 22 Deferred credits and other noncurrent liabilities 98 92 Total $ 152 $ 177

Contingencies and Commitments

Contingencies and Commitments	9 Months Ended
	Sep. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
Contingencies and Commitments	21. Contingencies and Commitments U. S. Steel is the subject of, or party to, a number of pending or threatened legal actions, contingencies and commitments involving a variety of matters, including laws and regulations relating to the environment. Certain of these matters are discussed below. The ultimate resolution of these contingencies could, individually or in the aggregate, be material to the Condensed Consolidated Financial Statements. However, management believes that U. S. Steel will remain a viable and competitive enterprise even though it is possible that these contingencies could be resolved unfavorably. U. S. Steel accrues for estimated costs related to existing lawsuits, claims and proceedings when it is probable that it will incur these costs in the future and the costs are reasonably estimable. Asbestos matters – As of September 30, 2021, U. S. Steel was a defendant in approximately 925 active cases involving approximately 2,515 plaintiffs. The vast majority of these cases involve multiple defendants. About 1,545, or approximately 61 percent, of these plaintiff claims are currently pending in a jurisdiction which permits filings with massive numbers of plaintiffs. At December 31, 2020, U. S. Steel was a defendant in approximately 855 cases involving approximately 2,445 plaintiffs. Based upon U. S. Steel’s experience in such cases, it believes that the actual number of plaintiffs who ultimately assert claims against U. S. Steel will likely be a small fraction of the total number of plaintiffs. The following table shows the number of asbestos claims in the current period and the prior three years: Period ended Opening Claims (a) New Claims Closing December 31, 2018 3,315 1,285 290 2,320 December 31, 2019 2,320 195 265 2,390 December 31, 2020 2,390 240 295 2,445 September 30, 2021 2,445 135 205 2,515 (a) The period ending December 31, 2018 includes approximately 1,000 dismissed cases previously pending in the State of Texas. The amount U. S. Steel accrues for pending asbestos claims is not material to U. S. Steel’s financial condition. However, U. S. Steel is unable to estimate the ultimate outcome of asbestos-related claims due to a number of uncertainties, including: (1) the rates at which new claims are filed, (2) the number of and effect of bankruptcies of other companies traditionally defending asbestos claims, (3) uncertainties associated with the variations in the litigation process from jurisdiction to jurisdiction, (4) uncertainties regarding the facts, circumstances and disease process with each claim, and (5) any new legislation enacted to address asbestos-related claims. Further, U. S. Steel does not believe that an accrual for unasserted claims is required. At any given reporting date, it is probable that there are unasserted claims that will be filed against the Company in the future. In 2020 and 2019, the Company engaged an outside valuation consultant to assist in assessing its ability to estimate an accrual for unasserted claims. This assessment was based on the Company's settlement experience, including recent claims trends. The analysis focused on settlements made over the last several years as these claims are likely to best represent future claim characteristics. After review by the valuation consultant and U. S. Steel management, it was determined that the Company could not estimate an accrual for unasserted claims. Despite these uncertainties, management believes that the ultimate resolution of these matters will not have a material adverse effect on U. S. Steel’s financial condition. Environmental matters – U. S. Steel is subject to federal, state, local and foreign laws and regulations relating to the environment. These laws generally provide for control of pollutants released into the environment and require responsible parties to undertake remediation of hazardous waste disposal sites. Penalties may be imposed for noncompliance. Changes in accrued liabilities for remediation activities where U. S. Steel is identified as a named party are summarized in the following table: (In millions) Nine Months Ended September 30, 2021 Beginning of period $ 146 Accruals for environmental remediation deemed probable and reasonably estimable 1 Obligations settled (23) End of period $ 124 Accrued liabilities for remediation activities are included in the following Condensed Consolidated Balance Sheet lines: (In millions) September 30, 2021 December 31, 2020 Accounts payable and other accrued liabilities $ 41 $ 43 Deferred credits and other noncurrent liabilities 83 103 Total $ 124 $ 146 Expenses related to remediation are recorded in cost of sales and were immaterial for both the nine-month periods ended September 30, 2021 and September 30, 2020. It is not currently possible to estimate the ultimate amount of all remediation costs that might be incurred or the penalties that may be imposed. Due to uncertainties inherent in remediation projects and the associated liabilities, it is reasonably possible that total remediation costs for active matters may exceed the accrued liabilities by as much as 45 to 70 percent. Remediation Projects U. S. Steel is involved in environmental remediation projects at or adjacent to several current and former U. S. Steel facilities and other locations that are in various stages of completion ranging from initial characterization through post-closure monitoring. Based on the anticipated scope and degree of uncertainty of projects, the Company categorizes projects as follows: (1) Projects with Ongoing Study and Scope Development - Projects which are still in the development phase. For these projects, the extent of remediation that may be required is not yet known, the remediation methods and plans are not yet developed, and/or cost estimates cannot be determined. Therefore, significant costs, in addition to the accrued liabilities for these projects, are reasonably possible. There are five environmental remediation projects where additional costs for completion are not currently estimable, but could be material. These projects are at Fairfield Works, Lorain Tubular, USS-UPI LLC (UPI) formerly known as USS-POSCO Industries, Duluth Works and the former steelmaking plant at Joliet, Illinois. As of September 30, 2021, accrued liabilities for these projects totaled $24 million for the costs of studies, investigations, interim measures, design and/or remediation. It is reasonably possible that additional liabilities associated with future requirements regarding studies, investigations, design and remediation for these projects could be as much as $50 million to $75 million. (2) Significant Projects with Defined Scope - Projects with significant accrued liabilities with a defined scope. As of September 30, 2021, there are two significant projects with defined scope greater than or equal to $5 million each, with a total accrued liability of $43 million. These projects are Gary Resource Conservation and Recovery Act (RCRA) (accrued liability of $24 million) and the former Geneva facility (accrued liability of $19 million). (3) Other Projects with a Defined Scope - Projects with relatively small accrued liabilities for which we believe that, while additional costs are possible, they are not likely to be significant, and also include those projects for which we do not yet possess sufficient information to estimate potential costs to U. S. Steel. There are three other environmental remediation projects which each had an accrued liability of between $1 million and $5 million. The total accrued liability for these projects at September 30, 2021 was $7 million. These projects have progressed through a significant portion of the design phase and material additional costs are not expected. The remaining environmental remediation projects each have an accrued liability of less than $1 million each. The total accrued liability for these projects at September 30, 2021 was approximately $3 million. The Company does not foresee material additional liabilities for any of these sites. Post-Closure Costs – Accrued liabilities for post-closure site monitoring and other costs at various closed landfills totaled $23 million at September 30, 2021 and were based on known scopes of work. Administrative and Legal Costs – As of September 30, 2021, U. S. Steel had an accrued liability of $13 million for administrative and legal costs related to environmental remediation projects. These accrued liabilities were based on projected administrative and legal costs for the next three years and do not change significantly from year to year. Capital Expenditures – For a number of years, U. S. Steel has made substantial capital expenditures to comply with various regulations, laws and other requirements relating to the environment. Such capital expenditures totaled $14 million and $8 million in the first nine months of 2021 and 2020, respectively. U. S. Steel anticipates making additional such expenditures in the future, which may be material; however, the exact amounts and timing of such expenditures are uncertain because of the continuing evolution of specific regulatory requirements. European Union (EU) Environmental Requirements - Phase IV of the EU Emissions Trading System (EU ETS) commenced on January 1, 2021 and will finish on December 31, 2030. The European Commission issued final approval of the Slovak National Allocation table in July 2021. The Slovak Ministry of Environment's decision on USSE’s free allocation for the first five years of the Phase IV period is expected by the end of 2021. In the fourth quarter of 2020 USSE started purchasing European Union Allowances (EUA) for the Phase IV period. As of September 30, 2021, we have pre-purchased approximately 3.3 million EUA totaling €134 million (approximately $155 million). The EU’s Industrial Emissions Directive requires implementation of EU-determined best available techniques (BAT) for Iron and Steel production to reduce environmental impacts as well as compliance with BAT associated emission levels. Total capital expenditures for projects to comply with or go beyond BAT requirements were €138 million (approximately $160 million) over the actual program period. These costs were partially offset by the EU funding received and may be mitigated over the next measurement periods if USSK complies with certain financial covenants, which are assessed annually. USSK complied with these covenants as of September 30, 2021. If we are unable to meet these covenants in the future, USSK might be required to provide additional collateral (e.g. bank guarantee) to secure 50 percent of the EU funding received. Environmental indemnifications – Throughout its history, U. S. Steel has sold numerous properties and businesses and many of these sales included indemnifications and cost sharing agreements related to the assets that were divested. The amount of potential environmental liability associated with these transactions and properties is not estimable due to the nature and extent of the unknown conditions related to the properties divested and deconsolidated. Aside from the environmental liabilities already recorded as a result of these transactions due to specific environmental remediation activities and cases (included in the $124 million of accrued liabilities for remediation discussed above), there are no other known probable and estimable environmental liabilities related to these transactions. Guarantees – The maximum guarantees of the indebtedness of unconsolidated entities of U. S. Steel totaled $7 million at September 30, 2021. Other contingencies – Under certain lease agreements covering various equipment, U. S. Steel has the option to renew the lease or to purchase the equipment at the end of the lease term. If U. S. Steel does not exercise the purchase option by the end of the lease term, U. S. Steel guarantees a residual value of the equipment as determined at the lease inception date (totaling approximately $14 million at September 30, 2021). No liability has been recorded for these guarantees as the potential loss is not probable. Insurance – U . S. Steel maintains insurance for certain property damage, equipment, business interruption and general liability exposures; however, insurance is applicable only after certain deductibles and retainages. U. S. Steel is self-insured for certain other exposures including workers’ compensation (where permitted by law) and auto liability. Liabilities are recorded for workers’ compensation and personal injury obligations. Other costs resulting from losses under deductible or retainage amounts or not otherwise covered by insurance are charged against income upon occurrence. U. S. Steel uses surety bonds, trusts and letters of credit to provide whole or partial financial assurance for certain obligations such as workers’ compensation. The total amount of active surety bonds, trusts and letters of credit being used for financial assurance purposes was approximately $214 million as of September 30, 2021, which reflects U. S. Steel’s maximum exposure under these financial guarantees, but not its total exposure for the underlying obligations. A significant portion of our trust arrangements and letters of credit are collateralized by the Credit Facility Agreement. The remaining trust arrangements and letters of credit are collateralized by restricted cash. Restricted cash, which is recorded in other current and noncurrent assets, totaled $100 million and $133 million at September 30, 2021 and December 31, 2020, respectively. Capital Commitments – At September 30, 2021, U. S. Steel’s contractual commitments to acquire property, plant and equipment totaled $687 million. Contractual Purchase Commitments – U. S. Steel is obligated to make payments under contractual purchase commitments, including unconditional purchase obligations. Payments for contracts with remaining terms in excess of one year are summarized below (in millions): Remainder of 2021 2022 2023 2024 2025 Later Total $299 $1,206 $557 $325 $315 $903 $3,605 The majority of U. S. Steel’s unconditional purchase obligations relates to the supply of industrial gases, and certain energy and utility services with terms ranging from two Total payments relating to unconditional purchase obligations were $215 million and $123 million for the three months ended September 30, 2021 and 2020, respectively, and $584 million and $425 million for the nine months ended September 30, 2021 and 2020, respectively.

Common Stock Issued

Common Stock Issued	9 Months Ended
	Sep. 30, 2021
Common Stock Issued [Abstract]
Common Stock Issued	22. Common Stock Issued In February 2021, U. S. Steel issued 48.3 million shares of common stock for net proceeds of approximately $790 million. In June 2020, U. S. Steel issued 50 million shares of common stock for net proceeds of approximately $410 million.

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2021
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events On October 1, 2021, U. S. Steel issued an irrevocable notice of redemption to redeem the entirety of its approximately $230 million aggregate principal amount of outstanding 6.250% Senior Notes due 2026 (2026 Senior Notes). The Company expects the total payment to the holders including the redemption premium to be approximately $237 million (reflecting a redemption price of 103.125% of the aggregate principal amount), plus accrued and unpaid interest to, but excluding, the redemption date of November 1, 2021. The 2026 Senior Notes will be redeemed with cash on hand. On October 15, 2021, U. S. Steel issued a notice of redemption to redeem approximately $70 million aggregate principal amount of its environmental revenue bonds. The Company expects the total payment to the holders including the redemption premium to be approximately $70 million (reflecting a redemption price of par), plus accrued and unpaid interest to, but excluding, the redemption date of December 1, 2021. These bonds will be redeemed with cash on hand.

New Accounting Standards (Polic

New Accounting Standards (Policies)	9 Months Ended
	Sep. 30, 2021
Accounting Changes and Error Corrections [Abstract]
New and Recently Adopted Accounting Standards	In August 2020, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update 2020-06, Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity (ASU 2020-06). ASU 2020-06 simplifies the accounting for certain financial instruments with characteristics of liabilities and equity, including convertible instruments and contracts on an entity’s own equity. ASU 2020-06 requires entities to provide expanded disclosures about the terms and features of convertible instruments and amends certain guidance in ASC 260 on the computation of EPS for convertible instruments and contracts on an entity’s own equity. ASU 2020-06 is effective for public companies for fiscal years beginning after December 15, 2021, and interim periods within those fiscal years, with early adoption of all amendments in the same period permitted. The Company is continuing to assess the impact of adoption of the ASU. In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740) - Simplifying the Accounting for Income Taxes (ASU 2019-12). ASU 2019-12 simplifies accounting for income taxes by removing certain exceptions from the general principles in Topic 740 including elimination of the exception to the incremental approach for intraperiod tax allocation when there is a loss from continuing operations and income or a gain from other items such as other comprehensive income. U. S. Steel adopted this guidance on January 1, 2021. The adoption of this guidance did not have a material impact on the Company's Condensed Consolidated Financial Statements.

Segment Information (Tables)

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2021
Segment Reporting [Abstract]
Results of Segment Operations	The results of segment operations for the three months ended September 30, 2021 and 2020 are: (In millions) Three Months Ended September 30, 2021 Customer Intersegment Net Earnings (loss) Earnings (loss) before interest and income taxes Flat-Rolled $ 3,541 $ 36 $ 3,577 $ 53 $ 1,015 Mini Mill 949 156 1,105 — 424 USSE 1,246 2 1,248 — 394 Tubular 216 6 222 4 — Total reportable segments 5,952 200 6,152 57 1,833 Other 12 9 21 — (2) Reconciling Items and Eliminations — (209) (209) — 511 Total $ 5,964 $ — $ 5,964 $ 57 $ 2,342 Three Months Ended September 30, 2020 Flat-Rolled $ 1,728 $ 71 $ 1,799 $ (3) $ (159) USSE 495 1 496 — 13 Tubular 96 — 96 — (52) Total reportable segments 2,319 72 2,391 (3) (198) Other 21 23 44 (28) (13) Reconciling Items and Eliminations — (95) (95) — — Total $ 2,340 $ — $ 2,340 $ (31) $ (211) The results of segment operations for the nine months ended September 30, 2021 and 2020 are: (In millions) Nine Months Ended September 30, 2021 Customer Intersegment Net Earnings (Loss) Earnings (loss) before interest and income taxes Flat-Rolled $ 8,804 $ 142 $ 8,946 $ 90 $ 1,740 Mini Mill 2,158 360 2,518 — 840 USSE 3,122 4 3,126 — 706 Tubular 534 13 547 10 (29) Total reportable segments 14,618 519 15,137 100 3,257 Other 35 65 100 6 20 Reconciling Items and Eliminations — (584) (584) — 524 Total $ 14,653 $ — $ 14,653 $ 106 $ 3,801 Nine Months Ended September 30, 2020 Flat-Rolled $ 5,199 $ 175 $ 5,374 $ (15) $ (523) USSE 1,403 3 1,406 — (27) Tubular 533 6 539 3 (147) Total reportable segments 7,135 184 7,319 (12) (697) Other 44 70 114 (66) (33) Reconciling Items and Eliminations — (254) (254) — (388) Total $ 7,179 $ — $ 7,179 $ (78) $ (1,118)
Schedule of Assets by Segment	A summary of total assets by segment is as follows: (In millions) September 30, 2021 December 31, 2020 Flat-Rolled $ 7,846 $ 7,099 Mini Mill 4,314 — USSE 6,116 5,502 Tubular 1,041 887 Total reportable segments $ 19,317 $ 13,488 Other $ 135 $ 911 Corporate, reconciling items, and eliminations (a) (2,119) (2,340) Total assets $ 17,333 $ 12,059 (a) The majority of Corporate, reconciling items, and eliminations total assets is comprised of cash and the elimination of intersegment amounts.
Schedule of Reconciling Items to EBIT	The following is a schedule of reconciling items to consolidated earnings before interest and income taxes: Three Months Ended September 30, Nine Months Ended September 30, (In millions) 2021 2020 2021 2020 Items not allocated to segments: Gain on previously held investment in Big River Steel $ — $ — $ 111 $ — Big River Steel - inventory step-up amortization — — (24) — Big River Steel - unrealized gains (losses) (a) 12 — (3) — Big River Steel - acquisition costs — — (9) — Gain on sale of Transtar (Note 5) 506 — 506 — Loss on USSE assets held for sale (7) — (7) — Restructuring and other charges (Note 20) — — (37) (130) Asset impairment charges (Note 1) — — (28) (263) Property Sale — — 15 — Gain on previously held investment in UPI — — — 25 Tubular inventory impairment charge — — — (24) December 24, 2018 Clairton coke making facility fire — — — 4 Total reconciling items $ 511 $ — $ 524 $ (388) (a) Big River Steel – unrealized losses represent the post-acquisition mark-to-market impacts of hedging instruments acquired with the purchase of the remaining equity interest in Big River Steel on January 15, 2021. See Note 14 for further details.

Acquisition (Tables)

Acquisition (Tables)	9 Months Ended
	Sep. 30, 2021
Business Combinations [Abstract]
Allocation of the Aggregate Purchase Price Based on Estimated Fair Values	The following table presents the preliminary allocation of the aggregate purchase price based on estimated fair values: (in millions) Assets Acquired: Receivables $ 166 Receivables with U. S. Steel (1) 99 Inventories 184 Other current assets 16 Property, plant and equipment 2,188 Intangibles 413 Goodwill 905 Other noncurrent assets 19 Total Assets Acquired $ 3,990 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 44 Deferred credits and other long-term liabilities 182 Total Liabilities Assumed $ 2,545 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 (1) The transaction to purchase Big River Steel included receivables for payments made by Big River Steel on behalf of U. S. Steel for retention bonuses of $22 million that impacted the previously held equity investment and for U. S. Steel liabilities assumed in the purchase of approximately $50 million. In addition, there were assumed receivables of approximately $27 million for steel substrate sales from Big River Steel to U. S. Steel. The receivables with U. S. Steel eliminate in consolidation with offsetting intercompany payables from U. S. Steel.
Unaudited Pro Forma Information for U. S. Steel Including the Results of the Big River Steel Acquisition	The following unaudited pro forma information for U. S. Steel includes the results of the Big River Steel acquisition as if it had been consummated on January 1, 2020. The unaudited pro forma information is based on historical information and is adjusted for amortization of the intangible asset, property, plant and equipment and debt fair value step-ups discussed above. Non-recurring acquisition related items included in the 2020 period include $111 million for the gain on previously held equity investment, $9 million in acquisition related costs and $24 million in inventory step-up amortization related to the purchase of the remaining interest in Big River Steel. In addition, costs for non-recurring retention bonuses of $44 million that occurred in January 2021 prior to the purchase of the remaining equity interest are included in the 2020 period. The pro forma information does not include any anticipated cost savings or other effects of the integration of Big River Steel. Accordingly, the unaudited pro forma information does not necessarily reflect the actual results that would have occurred, nor is it necessarily indicative of future results of operations. Pro forma adjustments were not tax-effected in 2020 as U. S. Steel had a full valuation allowance on its domestic deferred tax assets. Nine Months Ended September 30, (in millions) 2021 2020 Net sales $ 14,725 $ 7,849 Net earnings (loss) $ 3,034 $ (1,292)

Revenue (Tables)

Revenue (Tables)	9 Months Ended
	Sep. 30, 2021
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue by Product	Net Sales by Product (In millions): Three Months Ended September 30, 2021 Flat-Rolled Mini Mill USSE Tubular Other Total Semi-finished $ — $ — $ 35 $ — $ — $ 35 Hot-rolled sheets 887 571 657 — — 2,115 Cold-rolled sheets 1,037 159 145 — — 1,341 Coated sheets 1,216 219 356 — — 1,791 Tubular products — — 21 217 — 238 All Other (a) 401 — 32 (1) 12 444 Total $ 3,541 $ 949 $ 1,246 $ 216 $ 12 $ 5,964 (a) Consists primarily of sales of raw materials and coke making by-products. Three Months Ended September 30, 2020 Flat-Rolled USSE Tubular Other Total Semi-finished $ 5 $ — $ — $ — $ 5 Hot-rolled sheets 239 193 — — 432 Cold-rolled sheets 555 43 — — 598 Coated sheets 778 233 — — 1,011 Tubular products — 11 91 — 102 All Other (a) 151 15 5 21 192 Total $ 1,728 $ 495 $ 96 $ 21 $ 2,340 (a) Consists primarily of sales of raw materials and coke making by-products. Nine Months Ended September 30, 2021 Flat-Rolled Mini Mill USSE Tubular Other Total Semi-finished $ 12 $ — $ 84 $ — $ — $ 96 Hot-rolled sheets 1,990 1,271 1,604 — — 4,865 Cold-rolled sheets 2,710 365 330 — — 3,405 Coated sheets 3,114 519 988 — — 4,621 Tubular products — — 45 523 — 568 All Other (a) 978 3 71 11 35 1,098 Total $ 8,804 $ 2,158 $ 3,122 $ 534 $ 35 $ 14,653 (a) Consists primarily of sales of raw materials and coke making by-products. Nine Months Ended September 30, 2020 Flat-Rolled USSE Tubular Other Total Semi-finished $ 63 $ 2 $ — $ — $ 65 Hot-rolled sheets 980 544 — — 1,524 Cold-rolled sheets 1,495 114 — — 1,609 Coated sheets 2,202 664 — — 2,866 Tubular products — 31 520 — 551 All Other (a) 459 48 13 44 564 Total $ 5,199 $ 1,403 $ 533 $ 44 $ 7,179 (a) Consists primarily of sales of raw materials and coke making by-products.

Cash, Cash Equivalents and Re_2

Cash, Cash Equivalents and Restricted Cash (Tables)	9 Months Ended
	Sep. 30, 2021
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Schedule of Cash and Cash Equivalents	The following table provides a reconciliation of cash, cash equivalents and restricted cash reported within U. S. Steel's Condensed Consolidated Balance Sheets that sum to the total of the same amounts shown in the Condensed Consolidated Statement of Cash Flows: (In millions) September 30, 2021 September 30, 2020 Cash and cash equivalents $ 2,044 $ 1,696 Restricted cash in other current assets 17 2 Restricted cash in other noncurrent assets 91 89 Total cash, cash equivalents and restricted cash $ 2,152 $ 1,787
Schedule of Restricted Cash and Restricted Cash Equivalents	The following table provides a reconciliation of cash, cash equivalents and restricted cash reported within U. S. Steel's Condensed Consolidated Balance Sheets that sum to the total of the same amounts shown in the Condensed Consolidated Statement of Cash Flows: (In millions) September 30, 2021 September 30, 2020 Cash and cash equivalents $ 2,044 $ 1,696 Restricted cash in other current assets 17 2 Restricted cash in other noncurrent assets 91 89 Total cash, cash equivalents and restricted cash $ 2,152 $ 1,787

Inventories (Tables)

Inventories (Tables)	9 Months Ended
	Sep. 30, 2021
Inventory Disclosure [Abstract]
Inventories	(In millions) September 30, 2021 December 31, 2020 Raw materials $ 631 $ 416 Semi-finished products 1,055 633 Finished products 345 300 Supplies and sundry items 55 53 Total $ 2,086 $ 1,402

Intangible Assets (Tables)

Intangible Assets (Tables)	9 Months Ended
	Sep. 30, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
Amortizable Intangible Assets	Intangible assets that are being amortized on a straight-line basis over their estimated useful lives are detailed below: As of September 30, 2021 As of December 31, 2020 (In millions) Useful Gross Accumulated Net Gross Accumulated Impairment Accumulated Net Customer relationships 22 Years $ 413 $ 13 $ 400 $ 132 $ 55 $ 77 $ — Patents 5-15 Years 17 10 7 22 7 10 5 Energy Contract 10 Years 54 9 45 54 — 5 49 Other 4-15 Years — — — 14 5 9 — Total amortizable intangible assets $ 484 $ 32 $ 452 $ 222 $ 67 $ 101 $ 54
Summary of Goodwill by Segment	Below is a summary of goodwill by segment for the nine months ended September 30, 2021: Flat-Rolled Mini Mill USSE Tubular Total Balance at December 31, 2020 $ — $ — $ 4 $ — $ 4 Additions — 905 — — 905 Balance at September 30, 2021 $ — $ 905 $ 4 $ — $ 909

Pensions and Other Benefits (Ta

Pensions and Other Benefits (Tables)	9 Months Ended
	Sep. 30, 2021
Retirement Benefits [Abstract]
Net Periodic Benefit Cost	The following table reflects the components of net periodic benefit cost (income) for the three months ended September 30, 2021 and 2020: Pension Benefits Other Benefits (In millions) 2021 2020 2021 2020 Service cost $ 12 $ 13 $ 3 $ 3 Interest cost 41 49 13 16 Expected return on plan assets (91) (84) (21) (20) Amortization of prior service credit — — (7) (1) Amortization of actuarial net loss (gain) 29 36 (6) (4) Net periodic benefit cost (income), excluding below (9) 14 (18) (6) Multiemployer plans 19 19 — — Settlement, termination and curtailment losses (a) 5 2 — — Net periodic benefit cost (income) $ 15 $ 35 $ (18) $ (6) (a) During the three months ended September 30, 2021 and 2020, pension benefits incurred settlement charges of approximately $5 million and $2 million, respectively, due to lump sum payments to certain individuals. The following table reflects the components of net periodic benefit cost (income) for the nine months ended September 30, 2021 and 2020: Pension Benefits Other Benefits (In millions) 2021 2020 2021 2020 Service cost $ 40 $ 38 $ 9 $ 9 Interest cost 122 145 37 48 Expected return on plan assets (269) (249) (61) (60) Amortization of prior service cost 1 1 (21) (5) Amortization of actuarial net loss (gain) 104 108 (18) (12) Net periodic benefit cost (income), excluding below (2) 43 (54) (20) Multiemployer plans 56 58 — — Settlement, termination and curtailment losses (a) 8 10 — — Net periodic benefit cost (income) $ 62 $ 111 $ (54) $ (20) (a) During the nine months ended September 30, 2021, the pension plan incurred settlement and curtailment charges of approximately $8 million due to lump sum payments to certain individuals and the sale of Transtar. For the nine months ended September 30, 2020 the pension plan incurred settlement and special termination charges of approximately $10 million due to workforce restructuring and lump sum payments made to certain individuals.

Stock-Based Compensation Plans

Stock-Based Compensation Plans (Tables)	9 Months Ended
	Sep. 30, 2021
Share-based Payment Arrangement [Abstract]
Summary of Awards Made under Plans	The following table is a summary of the awards made under the Omnibus Plan during the first nine months of 2021 and 2020. 2021 2020 Grant Details Shares (a) Fair Value (b) Shares (a) Fair Value (b) Restricted Stock Units 1,831,880 $ 19.65 2,640,690 $ 8.82 Performance Awards (c) TSR 306,930 $ 19.46 671,390 $ 8.19 ROCE (d) 485,900 $ 17.92 — $ — (a) The share amounts shown in this table do not reflect an adjustment for estimated forfeitures. (b) Represents the per share weighted average for all grants during the period. (c) The number of performance awards shown represents the target share grant of the award. (d) The ROCE awards granted in 2020 and a portion of ROCE awards granted in 2021 are not shown in the table because they were granted in cash.

Earnings and Dividends Per Co_2

Earnings and Dividends Per Common Share (Tables)	9 Months Ended
	Sep. 30, 2021
Earnings Per Share [Abstract]
Computations for Basic and Diluted Earnings Per Common Share from Continuing Operations	Three Months Ended September 30, Nine Months Ended September 30, (Dollars in millions, except per share amounts) 2021 2020 2021 2020 Earnings (loss) attributable to United States Steel Corporation stockholders $ 2,002 $ (234) $ 3,105 $ (1,214) Weighted-average shares outstanding (in thousands): Basic 270,175 220,402 263,209 188,766 Effect of Senior Convertible Notes 12,199 — 11,082 — Effect of stock options, restricted stock units and performance awards 5,089 — 4,812 — Adjusted weighted-average shares outstanding, diluted 287,463 220,402 279,103 188,766 Basic earnings (loss) per common share $ 7.41 $ (1.06) $ 11.80 $ (6.43) Diluted earnings (loss) per common share $ 6.97 $ (1.06) $ 11.13 $ (6.43)

Derivative Instruments (Tables)

Derivative Instruments (Tables)	9 Months Ended
	Sep. 30, 2021
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Notional Amounts of Outstanding Derivative Positions	The table below shows the outstanding swap quantities used to hedge forecasted purchases and sales as of September 30, 2021 and September 30, 2020: Hedge Contracts Classification September 30, 2021 September 30, 2020 Natural gas (in mmbtus) Commodity purchase swaps 38,661,000 34,222,000 Tin (in metric tons) Commodity purchase swaps 1,384 787 Zinc (in metric tons) Commodity purchase swaps 12,853 8,148 Electricity (in megawatt hours) Commodity purchase swaps 909,240 847,680 Hot-rolled coils (in tons) Sales swaps 97,320 — Foreign currency (in millions of euros) Foreign exchange forwards € 290 € 240 Foreign currency (in millions of dollars) Foreign exchange forwards $ 9 $ — Foreign currency (in millions of CAD) Foreign exchange forwards $ — $ 8
Schedule of Effect of Hedge Accounting on Accumulated Other Comprehensive Income	The table below summarizes the effect of hedge accounting on Accumulated Other Comprehensive Income (AOCI) and amounts reclassified from AOCI into earnings for the three and nine months ended September 30, 2021 and 2020: Gain (Loss) on Derivatives in AOCI Amount of Gain (Loss) Recognized in Income (In millions) Three Months Ended September 30, 2021 Three Months Ended September 30, 2020 Location of Reclassification from AOCI (a) Three Months Ended September 30, 2021 Three Months Ended September 30, 2020 Sales swaps $ 52 $ — Net sales $ (60) $ — Commodity purchase swaps 20 19 Cost of sales (b) 14 (6) Foreign exchange forwards 8 (9) Cost of sales 1 (3) (a) The earnings impact of our hedging instruments substantially offsets the earnings impact of the related hedged items resulting in immaterial ineffectiveness. (b) Costs for commodity purchase swaps are recognized in cost of sales as products are sold. Gain (Loss) on Derivatives in AOCI Amount of Gain (Loss) Recognized in Income (In millions) Nine Months Ended September 30, 2021 Nine Months Ended September 30, 2020 Location of Reclassification from AOCI (a) Nine Months Ended September 30, 2021 Nine Months Ended September 30, 2020 Sales swaps $ (71) $ — Net sales $ (93) $ — Commodity purchase swaps 52 30 Cost of sales (b) 18 (26) Foreign exchange forwards 29 (8) Cost of sales (9) (2) (a) The earnings impact of our hedging instruments substantially offsets the earnings impact of the related hedged items resulting in immaterial ineffectiveness. (b) Costs for commodity purchase swaps are recognized in cost of sales as products are sold.

Debt (Tables)

Debt (Tables)	9 Months Ended
	Sep. 30, 2021
Debt Disclosure [Abstract]
Debt	(In millions) Issuer/Borrower Interest Maturity September 30, 2021 December 31, 2020 2037 Senior Notes U. S. Steel 6.650 2037 350 350 2029 Senior Secured Notes Big River Steel 6.625 2029 720 — 2029 Senior Notes U. S. Steel 6.875 2029 750 — 2026 Senior Notes U. S. Steel 6.250 2026 230 650 2026 Senior Convertible Notes U. S. Steel 5.000 2026 350 350 2025 Senior Notes U. S. Steel 6.875 2025 — 750 2025 Senior Secured Notes U. S. Steel 12.000 2025 — 1,056 Arkansas Teacher Retirement System Notes Payable Big River Steel 5.500 - 7.750 2023 106 — Export-Import Credit Agreement U. S. Steel Variable 2021 — 180 Environmental Revenue Bonds U. S. Steel 4.125 - 6.750 2024 - 2050 717 717 Environmental Revenue Bonds Big River Steel 4.500 - 4.750 2049 752 — Finance leases and all other obligations U. S. Steel Various 2021 - 2029 78 81 Finance leases and all other obligations Big River Steel Various 2021 - 2031 153 — Export Credit Agreement (ECA) U. S. Steel Variable 2031 136 113 Credit Facility Agreement U. S. Steel Variable 2024 — 500 Big River Steel ABL Facility Big River Steel Variable 2026 — — USSK Credit Agreement U. S. Steel Kosice Variable 2026 — 368 USSK Credit Facility U. S. Steel Kosice Variable 2021 — — Total Debt 4,342 5,115 Less unamortized discount, premium, and debt issuance costs 9 228 Less short-term debt, long-term debt due within one year, and short-term issuance costs 61 192 Long-term debt $ 4,272 $ 4,695
Summary of Debt Repayments	The following is a summary of debt repayments for our Senior Secured Notes, Senior Notes and Export-Import Credit Agreement made during the nine months ended September 30, 2021: Nine Months Ended September 30, 2021 Debt Instrument (in Millions) Date Debt Extinguished 6.250% Senior Notes due 2026 (a) Third quarter 2021 370 6.875% Senior Notes due 2025 (a) Third quarter 2021 718 6.625% 2029 Senior Secured Notes (a) Third quarter 2021 180 6.250% Senior Notes due 2026 Second quarter 2021 18 6.875% Senior Notes due 2025 Second quarter 2021 14 12.000% 2025 Senior Secured Notes (b) First quarter 2021 1,056 6.875% Senior Notes due 2025 First quarter 2021 18 6.250% Senior Notes due 2026 First quarter 2021 32 Export-Import Credit Agreement (c) First quarter 2021 180 Total $ 2,586 (a) During the three months ended September 30, 2021, there were redemption premiums paid of $28 million and a net gain of $5 million for the write-off of unamortized acquisition-related fair value adjustment, discounts, and debt issuance costs as a result of these debt repayments. (b) There were redemption premiums and unamortized discount and debt issuance write-offs of approximately $181 million and $71 million, respectively related to the repayment.
Summary of Debt Instrument Redemption Percentages	Year Redemption Price 2024 103.438 % 2025 101.719 % 2026 and thereafter 100.000 % Year Redemption Price 2023 103.313 % 2024 101.656 % 2025 and thereafter 100.000 % Year Redemption Price September 1, 2026 to August 31, 2027 103 % September 1, 2027 to August 31, 2028 102 % September 1, 2028 to August 31, 2029 101 % On and after September 1, 2029 100 % Year Redemption Price September 1, 2027 to August 31, 2028 103 % September 1, 2028 to August 31, 2029 102 % September 1, 2029 to August 31, 2030 101 % On and after September 1, 2030 100 %

Fair Value of Financial Instr_2

Fair Value of Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2021
Fair Value Disclosures [Abstract]
Financial Assets and Liabilities Not Carried at Fair Value	The following table summarizes U. S. Steel’s financial liabilities that were not carried at fair value at September 30, 2021 and December 31, 2020. The fair value of long-term debt was determined using Level 2 inputs. September 30, 2021 December 31, 2020 (In millions) Fair Carrying Fair Carrying Financial liabilities: Short-term and long-term debt (a) $ 4,663 $ 3,996 $ 5,323 $ 4,806 (a) Excludes finance lease obligations.

Statement of Changes in Stock_2

Statement of Changes in Stockholders' Equity (Tables)	9 Months Ended
	Sep. 30, 2021
Equity [Abstract]
Consolidated Statement of Changes in Equity	The following table reflects the first nine months of 2021 and 2020 reconciliation of the carrying amount of total equity, equity attributable to U. S. Steel and equity attributable to noncontrolling interests: Nine Months Ended September 30, 2021 (In millions) Total (Accumulated Deficit) Retained Earnings Accumulated Common Treasury Paid-in Non- Balance at beginning of year $ 3,879 $ (623) $ (47) $ 229 $ (175) $ 4,402 $ 93 Comprehensive income (loss): Net earnings 91 91 — — — — — Other comprehensive income (loss), net of tax: Pension and other benefit adjustments 24 — 24 — — — — Currency translation adjustment (47) — (47) — — — — Derivative financial instruments (20) — (20) — — — — Employee stock plans 6 — — 2 (7) 11 — Common Stock Issued 790 — — 48 — 742 — Dividends paid on common stock (3) — — — — (3) — Balance at March 31, 2021 $ 4,720 $ (532) $ (90) $ 279 $ (182) $ 5,152 $ 93 Comprehensive income (loss): Net earnings 1,012 1,012 — — — — — Other comprehensive income (loss), net of tax: Pension and other benefit adjustments 205 — 205 — — — — Currency translation adjustment 23 — 23 — — — — Derivative financial instruments (31) — (31) — — — — Employee stock plans 17 — — — (1) 18 — Dividends paid on common stock (2) — — — — (2) — Other (1) — — — — — (1) Balance at June 30, 2021 $ 5,943 $ 480 $ 107 $ 279 $ (183) $ 5,168 $ 92 Comprehensive income (loss): Net earnings 2,002 2,002 — — — — — Other comprehensive income (loss), net of tax: Pension and other benefit adjustments 15 — 15 — — — — Currency translation adjustment (26) — (26) — — — — Derivative financial instruments 60 — 60 — — — — Employee stock plans 16 — — (1) 17 — Dividends paid on common stock (3) (3) — — — — — Other 1 1 — — — — — Balance at September 30, 2021 $ 8,008 $ 2,480 $ 156 $ 279 $ (184) $ 5,185 $ 92 Nine Months Ended September 30, 2020 (In millions) Total Retained Earnings (Accumulated Deficit) Accumulated Common Treasury Paid-in Non- Balance at beginning of year $ 4,093 $ 544 $ (478) $ 179 $ (173) $ 4,020 $ 1 Comprehensive income (loss): Net loss (391) (391) — — — — — Other comprehensive income (loss), net of tax: Pension and other benefit adjustments 52 — 52 — — — — Currency translation adjustment (23) — (23) — — — — Derivative financial instruments (5) — (5) — — — — Employee stock plans 2 — — — (2) 4 — Dividends paid on common stock (2) (2) — — — — — Balance at March 31, 2020 $ 3,726 $ 151 $ (454) $ 179 $ (175) $ 4,024 $ 1 Comprehensive income (loss): Net loss (589) (589) — — — — — Other comprehensive income (loss), net of tax: Pension and other benefit adjustments 29 — 29 — — — — Currency translation adjustment 20 — 20 — — — — Derivative financial instruments 15 — 15 — — — — Employee stock plans 8 — — — — 8 — Common Stock Issued 410 — — 50 — 360 — Dividends paid on common stock (1) — — — — (1) — Stelco Option Agreement 37 — — — — — 37 Other (1) — — — — — (1) Balance at June 30, 2020 $ 3,654 $ (438) $ (390) $ 229 $ (175) $ 4,391 $ 37 Comprehensive income (loss): Net loss (234) (234) — — — — — Other comprehensive income (loss), net of tax: Pension and other benefit adjustments 16 — 16 — — — — Currency translation adjustment 34 — 34 — — — — Derivative financial instruments 8 — 8 — — — — Employee stock plans 10 — — — — 10 — Dividends paid on common stock (3) — — — — (3) — Stelco Option Agreement 18 — — — — — 18 Other 1 1 — — — — — Balance at September 30, 2020 $ 3,504 $ (671) $ (332) $ 229 $ (175) $ 4,398 $ 55

Reclassifications from Accumu_2

Reclassifications from Accumulated Other Comprehensive Income (AOCI) (Tables)	9 Months Ended
	Sep. 30, 2021
Equity [Abstract]
Other Comprehensive Income Activity Net of Tax	(In millions) Pension and Foreign Unrealized (Loss) Gain on Derivatives Total Balance at December 31, 2020 $ (458) $ 449 $ (38) $ (47) Other comprehensive income (loss) before reclassifications 190 (50) (49) 91 Amounts reclassified from AOCI (a) 54 — 58 112 Net current-period other comprehensive income (loss) 244 (50) 9 203 Balance at September 30, 2021 $ (214) $ 399 $ (29) $ 156 Balance at December 31, 2019 $ (843) $ 381 $ (16) $ (478) Other comprehensive income (loss) before reclassifications 6 31 (6) 31 Amounts reclassified from AOCI (a) 91 — 24 115 Net current-period other comprehensive income 97 31 18 146 Balance at September 30, 2020 $ (746) $ 412 $ 2 $ (332) (a) See table below for further details.
Defined Benefit Plan In other Comprehensive Income	Amount reclassified from AOCI (a) Three Months Ended September 30, Nine Months Ended September 30, Details about AOCI components (in millions) 2021 2020 2021 2020 Amortization of pension and other benefit items Prior service credits (a) $ (7) $ (1) $ (20) $ (4) Actuarial losses (a) 23 32 86 96 Settlement, termination and curtailment losses (a) 5 2 6 2 UPI Purchase Accounting Adjustment — — — 23 Total pensions and other benefits items 21 33 72 117 Derivative reclassifications to Condensed Consolidated Statements of Operations 40 6 77 28 Total before tax 61 39 149 145 Tax provision (15) (15) (37) (30) Net of tax $ 46 $ 24 $ 112 $ 115 (a) These AOCI components are included in the computation of net periodic benefit cost. See Note 10 for additional details.

Restructuring and Other Charg_2

Restructuring and Other Charges (Tables)	9 Months Ended
	Sep. 30, 2021
Restructuring and Related Activities [Abstract]
Schedule of Accrued Balances From Restructuring and Other Charges	The activity in the accrued balances incurred in relation to restructuring programs during the nine months ended September 30, 2021 were as follows: (In millions) Employee Related Costs Exit Costs Non-cash Charges Total Balance at December 31, 2020 $ 51 $ 126 $ — $ 177 Additional charges 3 33 1 37 Cash payments/utilization (a) (35) (26) (1) (62) Balance at September 30, 2021 $ 19 $ 133 $ — $ 152 (a) Payments of $8 million were made from the pension fund trust.
Schedule of Accrued Liabilities for Restructuring on Balance Sheet	Accrued liabilities for restructuring programs are included in the following balance sheet lines: (In millions) September 30, 2021 December 31, 2020 Accounts payable $ 35 $ 34 Payroll and benefits payable 6 29 Employee benefits 13 22 Deferred credits and other noncurrent liabilities 98 92 Total $ 152 $ 177

Contingencies and Commitments (

Contingencies and Commitments (Tables)	9 Months Ended
	Sep. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
Asbestos Litigation Activity	The following table shows the number of asbestos claims in the current period and the prior three years: Period ended Opening Claims (a) New Claims Closing December 31, 2018 3,315 1,285 290 2,320 December 31, 2019 2,320 195 265 2,390 December 31, 2020 2,390 240 295 2,445 September 30, 2021 2,445 135 205 2,515
Changes in Accrued Liabilities for Remediation Activities	Changes in accrued liabilities for remediation activities where U. S. Steel is identified as a named party are summarized in the following table: (In millions) Nine Months Ended September 30, 2021 Beginning of period $ 146 Accruals for environmental remediation deemed probable and reasonably estimable 1 Obligations settled (23) End of period $ 124
Accrued Liabilities for Remediation Activities Included in Balance Sheet	Accrued liabilities for remediation activities are included in the following Condensed Consolidated Balance Sheet lines: (In millions) September 30, 2021 December 31, 2020 Accounts payable and other accrued liabilities $ 41 $ 43 Deferred credits and other noncurrent liabilities 83 103 Total $ 124 $ 146
Payments for Contracts with Remaining Terms in Excess of One Year	Payments for contracts with remaining terms in excess of one year are summarized below (in millions): Remainder of 2021 2022 2023 2024 2025 Later Total $299 $1,206 $557 $325 $315 $903 $3,605

Basis of Presentation and Sig_2

Basis of Presentation and Significant Accounting Policies (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Accounting Policies [Abstract]
Asset impairment charges (Note 1)	$ 0	$ 28	$ 0	$ 28	$ 263

Segment Information - Additiona

Segment Information - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2021Segment
Segment Reporting [Abstract]
Number of reportable segments	4

Segment Information - Results o

Segment Information - Results of Segment Operations (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Segment Reporting Information [Line Items]
Revenues	$ 5,964	$ 2,340	$ 14,653	$ 7,179
Earnings (loss) from investees	57	(31)	106	(78)
Earnings (loss) before interest and income taxes	2,342	(211)	3,801	(1,118)
Flat-Rolled
Segment Reporting Information [Line Items]
Revenues	3,541	1,728	8,804	5,199
Earnings (loss) from investees	53	(3)	90	(15)
Earnings (loss) before interest and income taxes	1,015	(159)	1,740	(523)
Mini Mill
Segment Reporting Information [Line Items]
Revenues	949		2,158
Earnings (loss) from investees	0		0
Earnings (loss) before interest and income taxes	424		840
USSE
Segment Reporting Information [Line Items]
Revenues	1,246	495	3,122	1,403
Earnings (loss) from investees	0	0	0	0
Earnings (loss) before interest and income taxes	394	13	706	(27)
Tubular
Segment Reporting Information [Line Items]
Revenues	216	96	534	533
Earnings (loss) from investees	4	0	10	3
Earnings (loss) before interest and income taxes	0	(52)	(29)	(147)
Total reportable segments
Segment Reporting Information [Line Items]
Revenues	5,952	2,319	14,618	7,135
Earnings (loss) from investees	57	(3)	100	(12)
Earnings (loss) before interest and income taxes	1,833	(198)	3,257	(697)
Other
Segment Reporting Information [Line Items]
Revenues	12	21	35	44
Earnings (loss) from investees	0	(28)	6	(66)
Earnings (loss) before interest and income taxes	(2)	(13)	20	(33)
Intersegment Sales
Segment Reporting Information [Line Items]
Revenues	(209)	(95)	(584)	(254)
Intersegment Sales | Flat-Rolled
Segment Reporting Information [Line Items]
Revenues	36	71	142	175
Intersegment Sales | Mini Mill
Segment Reporting Information [Line Items]
Revenues	156		360
Intersegment Sales | USSE
Segment Reporting Information [Line Items]
Revenues	2	1	4	3
Intersegment Sales | Tubular
Segment Reporting Information [Line Items]
Revenues	6	0	13	6
Intersegment Sales | Total reportable segments
Segment Reporting Information [Line Items]
Revenues	200	72	519	184
Intersegment Sales | Other
Segment Reporting Information [Line Items]
Revenues	9	23	65	70
Net Sales
Segment Reporting Information [Line Items]
Revenues	5,964	2,340	14,653	7,179
Net Sales | Flat-Rolled
Segment Reporting Information [Line Items]
Revenues	3,577	1,799	8,946	5,374
Net Sales | Mini Mill
Segment Reporting Information [Line Items]
Revenues	1,105		2,518
Net Sales | USSE
Segment Reporting Information [Line Items]
Revenues	1,248	496	3,126	1,406
Net Sales | Tubular
Segment Reporting Information [Line Items]
Revenues	222	96	547	539
Net Sales | Total reportable segments
Segment Reporting Information [Line Items]
Revenues	6,152	2,391	15,137	7,319
Net Sales | Other
Segment Reporting Information [Line Items]
Revenues	21	44	100	114
Reconciling Items and Eliminations
Segment Reporting Information [Line Items]
Revenues	(209)	(95)	(584)	(254)
Earnings (loss) from investees	0	0	0	0
Earnings (loss) before interest and income taxes	$ 511	$ 0	$ 524	$ (388)

Segment Information - Schedule

Segment Information - Schedule of Assets by Segment (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ 17,333	$ 12,059
Corporate, reconciling items, and eliminations
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	(2,119)	(2,340)
Flat-Rolled
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	7,846	7,099
Mini Mill
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	4,314	0
USSE
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	6,116	5,502
Tubular
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	1,041	887
Total reportable segments
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	19,317	13,488
Other
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ 135	$ 911

Segment Information - Schedul_2

Segment Information - Schedule of Reconciling Items to Income (Loss) from Operations (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Other items not allocated to segment
Total reconciling items	$ 2,342	$ (211)	$ 3,801	$ (1,118)
Reconciling Items and Eliminations
Other items not allocated to segment
Total reconciling items	511	0	524	(388)
Restructuring Charges | Reconciling Items and Eliminations
Other items not allocated to segment
Total reconciling items	0	0	(37)	(130)
Asset Impairment Charges | Reconciling Items and Eliminations
Other items not allocated to segment
Total reconciling items	0	0	(28)	(263)
Property Sale | Reconciling Items and Eliminations
Other items not allocated to segment
Total reconciling items	0	0	15	0
Big River Steel | Gain on Previously Held Investment | Reconciling Items and Eliminations
Other items not allocated to segment
Total reconciling items	0	0	111	0
Big River Steel | Inventory Step-Up Amortization | Reconciling Items and Eliminations
Other items not allocated to segment
Total reconciling items	0	0	(24)	0
Big River Steel | Unrealized Losses | Reconciling Items and Eliminations
Other items not allocated to segment
Total reconciling items	12	0	(3)	0
Big River Steel | Acquisition Costs | Reconciling Items and Eliminations
Other items not allocated to segment
Total reconciling items	0	0	(9)	0
Transtar, LLC | Gain on Sale of Business | Reconciling Items and Eliminations
Other items not allocated to segment
Total reconciling items	506	0	506	0
USSE | Loss on Assets Held For Sale | Reconciling Items and Eliminations
Other items not allocated to segment
Total reconciling items	(7)	0	(7)	0
UPI | Gain on Previously Held Investment | Reconciling Items and Eliminations
Other items not allocated to segment
Total reconciling items	0	0	0	25
Tubular products | Tubular Inventory Adjustment | Reconciling Items and Eliminations
Other items not allocated to segment
Total reconciling items	0	0	0	(24)
Clairton | Fire | Reconciling Items and Eliminations
Other items not allocated to segment
Total reconciling items	$ 0	$ 0	$ 0	$ 4

Acquisition - Allocation of the

Acquisition - Allocation of the Aggregate Purchase Price Based on Estimated Fair Values (Details) - USD ($) $ in Millions	Jan. 15, 2021	Sep. 30, 2021	Dec. 31, 2020
Assets Acquired:
Goodwill		$ 909	$ 4
Big River Steel
Assets Acquired:
Receivables	$ 166
Receivables with U. S. Steel (1)	99
Inventories	184
Other current assets	16
Property, plant and equipment	2,188
Intangibles	413
Goodwill	905
Other noncurrent assets	19
Total Assets Acquired	3,990
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	44
Deferred credits and other long-term liabilities	182
Total Liabilities Assumed	2,545
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

Acquisition - Unaudited Pro For

Acquisition - Unaudited Pro Forma Information for U. S. Steel Including the Results of the Big River Steel Acquisition (Details) - Big River Steel - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Business Acquisition [Line Items]
Net sales	$ 14,725	$ 7,849
Net earnings (loss)	$ 3,034	$ (1,292)

Acquisition - Narrative (Detail

Acquisition - Narrative (Details) - USD ($) $ in Millions	Jul. 28, 2021	Jan. 15, 2021	Feb. 29, 2020	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Oct. 31, 2019
Business Acquisition [Line Items]
Gain on sale of Transtar				$ 506	$ 0	$ 506	$ 0
Customer relationships
Business Acquisition [Line Items]
Useful life						22 years
Energy Contract
Business Acquisition [Line Items]
Useful life						10 years
Big River Steel
Business Acquisition [Line Items]
Purchase price, net of cash acquired		$ 625
Cash received in acquisition		36
Restricted cash received in acquisition		62
Liabilities assumed		50
Transaction Fees		9
Ownership interest acquired								49.90%
Fair value of previously held investment		770
Remeasurement gain		111
Step-up to fair value for property, plant and equipment		308
Step-up to fair value for debt		194
Step-up to fair value for inventory		24
Goodwill recorded		$ 905
Risk Adjusted Rate		11.00%
Terminal Growth Rate		2.00%
Gain on previously held equity investment included in pro forma information							111
Transaction fees and other related costs included in pro forma information							9
Inventory step-up amortization included in pro forma information							24
Non-recurring retention bonuses included in pro forma information							$ 44
Accounts payable and accrued liabilities		$ 224
Current portion of long-term debt		1,997
Property, plant and equipment		2,188
Big River Steel | Customer relationships
Business Acquisition [Line Items]
Intangible asset recorded		$ 413
Amortization period for intangible asset		22 years
USS-POSCO Industries (UPI)
Business Acquisition [Line Items]
Purchase price, net of cash acquired			$ 3
Cash received in acquisition			2
Fair value of previously held investment			5
Remeasurement gain			25
UPI accounts payable for substrate purchased from U. S. Steel			135
Receivables			44
Inventories			96
Accounts payable and accrued liabilities			19
Current portion of long-term debt			55
Payroll and employee benefits liabilities			78
Property, plant and equipment			97
Step-up to fair value for property, plant and equipment			47
Step-up to fair value for intangible asset for a beneficial energy contract			$ 54
USS-POSCO Industries (UPI) | Energy Contract
Business Acquisition [Line Items]
Useful life			10 years
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Transtar, LLC
Business Acquisition [Line Items]
Percentage of ownership before transaction	100.00%
Disposal group, cash purchase price	$ 627
Gain on sale of Transtar				$ 506

Revenue - Disaggregation of Rev

Revenue - Disaggregation of Revenue by Product (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disaggregation of Revenue [Line Items]
Revenues	$ 5,964	$ 2,340	$ 14,653	$ 7,179
Semi-finished
Disaggregation of Revenue [Line Items]
Revenues	35	5	96	65
Hot-rolled sheets
Disaggregation of Revenue [Line Items]
Revenues	2,115	432	4,865	1,524
Cold-rolled sheets
Disaggregation of Revenue [Line Items]
Revenues	1,341	598	3,405	1,609
Coated sheets
Disaggregation of Revenue [Line Items]
Revenues	1,791	1,011	4,621	2,866
Tubular products
Disaggregation of Revenue [Line Items]
Revenues	238	102	568	551
All Other
Disaggregation of Revenue [Line Items]
Revenues	444	192	1,098	564
Flat-Rolled
Disaggregation of Revenue [Line Items]
Revenues	3,541	1,728	8,804	5,199
Flat-Rolled | Semi-finished
Disaggregation of Revenue [Line Items]
Revenues	0	5	12	63
Flat-Rolled | Hot-rolled sheets
Disaggregation of Revenue [Line Items]
Revenues	887	239	1,990	980
Flat-Rolled | Cold-rolled sheets
Disaggregation of Revenue [Line Items]
Revenues	1,037	555	2,710	1,495
Flat-Rolled | Coated sheets
Disaggregation of Revenue [Line Items]
Revenues	1,216	778	3,114	2,202
Flat-Rolled | Tubular products
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Flat-Rolled | All Other
Disaggregation of Revenue [Line Items]
Revenues	401	151	978	459
Mini Mill
Disaggregation of Revenue [Line Items]
Revenues	949		2,158
Mini Mill | Semi-finished
Disaggregation of Revenue [Line Items]
Revenues	0		0
Mini Mill | Hot-rolled sheets
Disaggregation of Revenue [Line Items]
Revenues	571		1,271
Mini Mill | Cold-rolled sheets
Disaggregation of Revenue [Line Items]
Revenues	159		365
Mini Mill | Coated sheets
Disaggregation of Revenue [Line Items]
Revenues	219		519
Mini Mill | Tubular products
Disaggregation of Revenue [Line Items]
Revenues	0		0
Mini Mill | All Other
Disaggregation of Revenue [Line Items]
Revenues	0		3
USSE
Disaggregation of Revenue [Line Items]
Revenues	1,246	495	3,122	1,403
USSE | Semi-finished
Disaggregation of Revenue [Line Items]
Revenues	35	0	84	2
USSE | Hot-rolled sheets
Disaggregation of Revenue [Line Items]
Revenues	657	193	1,604	544
USSE | Cold-rolled sheets
Disaggregation of Revenue [Line Items]
Revenues	145	43	330	114
USSE | Coated sheets
Disaggregation of Revenue [Line Items]
Revenues	356	233	988	664
USSE | Tubular products
Disaggregation of Revenue [Line Items]
Revenues	21	11	45	31
USSE | All Other
Disaggregation of Revenue [Line Items]
Revenues	32	15	71	48
Tubular
Disaggregation of Revenue [Line Items]
Revenues	216	96	534	533
Tubular | Semi-finished
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Tubular | Hot-rolled sheets
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Tubular | Cold-rolled sheets
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Tubular | Coated sheets
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Tubular | Tubular products
Disaggregation of Revenue [Line Items]
Revenues	217	91	523	520
Tubular | All Other
Disaggregation of Revenue [Line Items]
Revenues	(1)	5	11	13
Other
Disaggregation of Revenue [Line Items]
Revenues	12	21	35	44
Other | Semi-finished
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Other | Hot-rolled sheets
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Other | Cold-rolled sheets
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Other | Coated sheets
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Other | Tubular products
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Other | All Other
Disaggregation of Revenue [Line Items]
Revenues	$ 12	$ 21	$ 35	$ 44

Cash, Cash Equivalents and Re_3

Cash, Cash Equivalents and Restricted Cash - Schedule of Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020	Dec. 31, 2019
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	$ 2,044	$ 1,985	$ 1,696
Restricted cash in other current assets	17		2
Restricted cash in other noncurrent assets	91	130	89
Total cash, cash equivalents and restricted cash	$ 2,152	$ 2,118	$ 1,787	$ 939

Inventories - Inventory Disclos

Inventories - Inventory Disclosure (Detail) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Inventory Disclosure [Abstract]
Raw materials	$ 631	$ 416
Semi-finished products	1,055	633
Finished products	345	300
Supplies and sundry items	55	53
Total	$ 2,086	$ 1,402

Inventories - Additional Inform

Inventories - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Inventory Disclosure [Abstract]
Percent of Last-in, First-out (LIFO) inventory to total inventory values	44.00%		44.00%		59.00%
Estimate in excess of current acquisition costs over stated inventory values	$ 1,012		$ 1,012		$ 848
Cost of sales increase (reduction), liquidations of LIFO inventories	$ 5	$ 11	$ 12	$ 5

Intangible Assets - Amortizable

Intangible Assets - Amortizable Intangible Assets (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 484	$ 222
Accumulated Impairment		67
Accumulated Amortization	32	101
Net Amount	$ 452	54
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Useful Lives	22 years
Gross Carrying Amount	$ 413	132
Accumulated Impairment		55
Accumulated Amortization	13	77
Net Amount	400	0
Patents
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	17	22
Accumulated Impairment		7
Accumulated Amortization	10	10
Net Amount	$ 7	5
Patents | Minimum
Finite-Lived Intangible Assets [Line Items]
Useful Lives	5 years
Patents | Maximum
Finite-Lived Intangible Assets [Line Items]
Useful Lives	15 years
Energy Contract
Finite-Lived Intangible Assets [Line Items]
Useful Lives	10 years
Gross Carrying Amount	$ 54	54
Accumulated Impairment		0
Accumulated Amortization	9	5
Net Amount	45	49
Other
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	0	14
Accumulated Impairment		5
Accumulated Amortization	0	9
Net Amount	$ 0	$ 0
Other | Minimum
Finite-Lived Intangible Assets [Line Items]
Useful Lives	4 years
Other | Maximum
Finite-Lived Intangible Assets [Line Items]
Useful Lives	15 years

Intangible Assets - Goodwill (D

Intangible Assets - Goodwill (Details) $ in Millions	9 Months Ended
	Sep. 30, 2021USD ($)
Goodwill [Line Items]
Balance at December 31, 2020	$ 4
Additions	905
Balance at September 30, 2021	909
Flat-Rolled
Goodwill [Line Items]
Balance at December 31, 2020	0
Additions	0
Balance at September 30, 2021	0
Mini Mill
Goodwill [Line Items]
Balance at December 31, 2020	0
Additions	905
Balance at September 30, 2021	905
USSE
Goodwill [Line Items]
Balance at December 31, 2020	4
Additions	0
Balance at September 30, 2021	4
Tubular
Goodwill [Line Items]
Balance at December 31, 2020	0
Additions	0
Balance at September 30, 2021	$ 0

Intangible Assets - Additional

Intangible Assets - Additional Information (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Indefinite-lived Intangible Assets [Line Items]
Estimated amortization expense for the remainder of 2021	$ 6
Estimated amortization expense for 2022	125
Estimated amortization expense for 2023	125
Estimated amortization expense for 2024	125
Estimated amortization expense for 2025	125
Estimated amortization expense for 2026	125
Estimated amortization expense for thereafter	320
Use Rights
Indefinite-lived Intangible Assets [Line Items]
Carrying amount of acquired water rights with indefinite lives	$ 75	$ 75

Pensions and Other Benefits - N

Pensions and Other Benefits - Net Periodic Benefit Costs (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 12	$ 13	$ 40	$ 38
Interest cost	41	49	122	145
Expected return on plan assets	(91)	(84)	(269)	(249)
Amortization of prior service credit	0	0	1	1
Amortization of actuarial net loss (gain)	29	36	104	108
Net periodic benefit cost (income), excluding below	(9)	14	(2)	43
Multiemployer plans	19	19	56	58
Settlement, termination and curtailment losses (a)	5	2	8	10
Net periodic benefit cost (income)	15	35	62	111
Pension Benefits | Employee Related Costs
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Settlement, termination and curtailment losses (a)	(5)	(2)	8	10
Other Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	3	3	9	9
Interest cost	13	16	37	48
Expected return on plan assets	(21)	(20)	(61)	(60)
Amortization of prior service credit	(7)	(1)	(21)	(5)
Amortization of actuarial net loss (gain)	(6)	(4)	(18)	(12)
Net periodic benefit cost (income), excluding below	(18)	(6)	(54)	(20)
Multiemployer plans	0	0	0	0
Settlement, termination and curtailment losses (a)	0	0	0	0
Net periodic benefit cost (income)	$ (18)	$ (6)	$ (54)	$ (20)

Pensions and Other Benefits - A

Pensions and Other Benefits - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Jun. 30, 2021	Sep. 30, 2021	Sep. 30, 2020
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Cash contribution by employer to defined contribution plans	$ 11	$ 1		$ 32	$ 16
Steelworkers Pension Trust
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Employer contributions, defined benefit plan				56
Other Pension Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Employer contributions, defined benefit plan				10
Unfunded Other Postretirement Benefit Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Cash contribution by employer for other postretirement benefits not funded by trusts				$ 31
Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Remeasurment impact			$ 255
Funded status percentage			103.00%

Stock-Based Compensation Plan_2

Stock-Based Compensation Plans - Summary of Awards Made under Plans (Detail) - $ / shares	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, other than stock options (in shares)	1,831,880	2,640,690
Grant date fair value per share of awards other than stock options (in dollars per share)	$ 19.65	$ 8.82
Total Shareholder Return (TSR) Performance Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, other than stock options (in shares)	306,930	671,390
Grant date fair value per share of awards other than stock options (in dollars per share)	$ 19.46	$ 8.19
Return On Capital Employed (ROCE) Performance Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, other than stock options (in shares)	485,900	0
Grant date fair value per share of awards other than stock options (in dollars per share)	$ 17.92	$ 0

Stock-Based Compensation Plan_3

Stock-Based Compensation Plans - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense recognized	$ 15	$ 8	$ 41	$ 20
Unrecognized compensation costs related to non-vested stocks	$ 46		$ 46
Weighted average period for recognizing non-vested stock-based compensation costs			16 months
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation plans, award vesting period			3 years
Total Shareholder Return (TSR) Performance Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation plans, award vesting period			3 years
Performance Period Weighting Year One, Year Two, Year Three (Individually)			20.00%
Performance Period Weighting All Three Years			40.00%
Total Shareholder Return (TSR) Performance Awards | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting of performance awards as percentage to target award			0.00%
Total Shareholder Return (TSR) Performance Awards | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting of performance awards as percentage to target award			200.00%
Return On Capital Employed (ROCE) Performance Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation plans, award vesting period			3 years
Return On Capital Employed (ROCE) Performance Awards | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting of performance awards as percentage to target award			0.00%
Return On Capital Employed (ROCE) Performance Awards | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting of performance awards as percentage to target award			200.00%
Omnibus Incentive Compensation Plan 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate number of shares to be issued	32,700,000		32,700,000
Number of shares available for future grants	15,966,607		15,966,607

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Income Tax Disclosure [Abstract]
Tax provision	$ 260	$ (24)	$ 224	$ (48)
Additional benefit related to reversal of valuation allowance			$ 514
Discrete benefit related to accounting exception				39
Expense related to an updated estimate to tax reserves related to an unrecognized tax benefit				$ 13

Earnings and Dividends Per Co_3

Earnings and Dividends Per Common Share - Computations for Basic and Diluted Income (Loss) Per Common Share from Continuing Operations (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Earnings Per Share [Abstract]
Earnings (loss) attributable to United States Steel Corporation stockholders	$ 2,002	$ (234)	$ 3,105	$ (1,214)
Weighted-average shares outstanding (in thousands):
Basic (in shares)	270,175	220,402	263,209	188,766
Effect of Senior Convertible Notes (in shares)	12,199	0	11,082	0
Effect of stock options, restricted stock units and performance awards (in shares)	5,089	0	4,812	0
Adjusted weighted-average shares outstanding, diluted (in shares)	287,463	220,402	279,103	188,766
Basic (loss) earnings per common share (in dollars per share)	$ 7.41	$ (1.06)	$ 11.80	$ (6.43)
Diluted (loss) earnings per common share (in dollars per share)	$ 6.97	$ (1.06)	$ 11.13	$ (6.43)

Earnings and Dividends Per Co_4

Earnings and Dividends Per Common Share - Additional Information (Details) - $ / shares shares in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Quarterly dividend per common share (in dollars per share)	$ 0.01	$ 0.01	$ 0.01	$ 0.01	$ 0.01	$ 0.01
Securities Granted under the Ominibus Plan
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities excluded from the computation of diluted EPS (in shares)	600			5,700			1,200	5,500

Derivative Instruments - Schedu

Derivative Instruments - Schedule of Notional Amounts of Outstanding Derivative Positions (Detail) - Cash flow hedges MMBTU in Thousands, € in Millions, $ in Millions, $ in Millions	Sep. 30, 2021EUR (€)TMMBTU	Sep. 30, 2021USD ($)TMMBTU	Sep. 30, 2021CAD ($)TMMBTU	Sep. 30, 2020EUR (€)TMMBTU	Sep. 30, 2020USD ($)TMMBTU	Sep. 30, 2020CAD ($)TMMBTU
Foreign exchange forwards
Derivative [Line Items]
Notional amount of derivatives	€ 290	$ 9	$ 0	€ 240	$ 0	$ 8
Natural gas (in mmbtus) | Commodity purchase swaps
Derivative [Line Items]
Quantities of derivatives held | MMBTU	38,661	38,661	38,661	34,222	34,222	34,222
Tin (in metric tons) | Commodity purchase swaps
Derivative [Line Items]
Quantities of derivatives held	1,384	1,384	1,384	787	787	787
Zinc (in metric tons) | Commodity purchase swaps
Derivative [Line Items]
Quantities of derivatives held	12,853	12,853	12,853	8,148	8,148	8,148
Electricity (in megawatt hours) | Commodity purchase swaps
Derivative [Line Items]
Quantities of derivatives held	909,240	909,240	909,240	847,680	847,680	847,680
Hot-rolled coils (in tons) | Sales swaps
Derivative [Line Items]
Quantities of derivatives held	97,320	97,320	97,320	0	0	0

Derivative Instruments - Sche_2

Derivative Instruments - Schedule of Effect of Hedge Accounting on Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Sales swaps
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives in AOCI	$ 52	$ 0	$ (71)	$ 0
Commodity purchase swaps
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives in AOCI	20	19	52	30
Foreign exchange forwards
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives in AOCI	8	(9)	29	(8)
Net sales | Sales swaps
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in income	(60)	0	(93)	0
Cost of sales | Commodity purchase swaps
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in income	14	(6)	18	(26)
Cost of sales | Foreign exchange forwards
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in income	$ 1	$ (3)	$ (9)	$ (2)

Derivative Instruments - Additi

Derivative Instruments - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Accounts Receivable | Cash flow hedges
Derivative [Line Items]
Derivative Instruments in Hedges, Assets, at Fair Value	$ 68		$ 68		$ 5
Accounts payable | Cash flow hedges
Derivative [Line Items]
Derivative Instruments in Hedges, Liabilities, at Fair Value	103		103		$ 54
Not Designated as Hedging Instrument | Accounts Receivable | Cash flow hedges
Derivative [Line Items]
Derivative asset	13		13
Not Designated as Hedging Instrument | Accounts payable | Cash flow hedges
Derivative [Line Items]
Derivative liability	2		$ 2
Foreign exchange forwards
Derivative [Line Items]
Derivatives, term of contract			13 months
Commodity purchase swaps | Designated as Hedging Instrument
Derivative [Line Items]
Derivatives, term of contract			15 months
Commodity purchase swaps | Not Designated as Hedging Instrument
Derivative [Line Items]
Derivatives, term of contract			27 months
Sales swaps
Derivative [Line Items]
Derivatives, term of contract			3 months
Cost of sales
Derivative [Line Items]
Derivative in AOCI to be recognized in income within 1 year			$ 62
Cost of sales | Foreign exchange forwards
Derivative [Line Items]
Amount of gain (loss) recognized in income	1	$ (3)	(9)	$ (2)
Cost of sales | Commodity purchase swaps
Derivative [Line Items]
Amount of gain (loss) recognized in income	14	(6)	18	(26)
Cost of sales | Sales swaps | Not Designated as Hedging Instrument
Derivative [Line Items]
Amount of gain (loss) recognized in income	12		3
Net sales
Derivative [Line Items]
Derivative in AOCI to be recognized in income within 1 year			97
Net sales | Sales swaps
Derivative [Line Items]
Amount of gain (loss) recognized in income	$ (60)	$ 0	$ (93)	$ 0

Debt - Schedule of Debt (Detail

Debt - Schedule of Debt (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2021	Feb. 11, 2021	Dec. 31, 2020	Sep. 18, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Debt and finance lease obligation	$ 4,342		$ 5,115
Less unamortized discount, premium, and debt issuance costs	9		228
Less short-term debt, long-term debt due within one year, and short-term issuance costs	61		192
Long-term debt	$ 4,272		4,695
2037 Senior Notes
Debt Instrument [Line Items]
Interest rate	6.65%
Debt and finance lease obligation	$ 350		350
2029 Senior Secured Notes
Debt Instrument [Line Items]
Interest rate	6.625%			6.625%
Debt and finance lease obligation	$ 720		0
2029 Senior Notes
Debt Instrument [Line Items]
Interest rate	6.875%	6.875%
Debt and finance lease obligation	$ 750		0
2026 Senior Notes
Debt Instrument [Line Items]
Interest rate	6.25%
Debt and finance lease obligation	$ 230		650
2026 Senior Convertible Notes
Debt Instrument [Line Items]
Interest rate	5.00%
Debt and finance lease obligation	$ 350		350
2025 Senior Notes
Debt Instrument [Line Items]
Interest rate	6.875%
Debt and finance lease obligation	$ 0		750
2025 Senior Secured Notes
Debt Instrument [Line Items]
Interest rate	12.00%
Debt and finance lease obligation	$ 0		1,056
Arkansas Teacher Retirement System Notes Payable
Debt Instrument [Line Items]
Debt and finance lease obligation	$ 106		0
Arkansas Teacher Retirement System Notes Payable | Minimum
Debt Instrument [Line Items]
Interest rate	5.50%				5.50%
Arkansas Teacher Retirement System Notes Payable | Maximum
Debt Instrument [Line Items]
Interest rate	7.75%				7.75%
Export-Import Credit Agreement
Debt Instrument [Line Items]
Interest rate description	Variable
Debt and finance lease obligation	$ 0		180
Environmental Revenue Bonds
Debt Instrument [Line Items]
Debt and finance lease obligation	$ 717		717
Environmental Revenue Bonds | Minimum
Debt Instrument [Line Items]
Interest rate	4.125%
Environmental Revenue Bonds | Maximum
Debt Instrument [Line Items]
Interest rate	6.75%
Environmental Revenue Bonds
Debt Instrument [Line Items]
Debt and finance lease obligation	$ 752		0
Environmental Revenue Bonds | Minimum
Debt Instrument [Line Items]
Interest rate	4.50%
Environmental Revenue Bonds | Maximum
Debt Instrument [Line Items]
Interest rate	4.75%
Finance leases and all other obligations
Debt Instrument [Line Items]
Interest rate description	Various
Debt and finance lease obligation	$ 78		81
Finance leases and all other obligations
Debt Instrument [Line Items]
Interest rate description	Various
Debt and finance lease obligation	$ 153		0
Export Credit Agreement (ECA)
Debt Instrument [Line Items]
Interest rate description	Variable
Debt and finance lease obligation	$ 136		113
Credit Facility Agreement
Debt Instrument [Line Items]
Interest rate description	Variable
Debt and finance lease obligation	$ 0		500
Big River Steel ABL Facility
Debt Instrument [Line Items]
Interest rate description	Variable
Debt and finance lease obligation	$ 0		0
USSK Credit Agreement
Debt Instrument [Line Items]
Interest rate description	Variable
Debt and finance lease obligation	$ 0		368
USSK Credit Facility
Debt Instrument [Line Items]
Interest rate description	Variable
Debt and finance lease obligation	$ 0		$ 0

Debt - Summary of Debt Repaymen

Debt - Summary of Debt Repayments (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2021	Sep. 18, 2020
Debt Instrument [Line Items]
Debt Extinguished				$ 2,586
Cash Gain (Loss) on Extinguishment of Debt	$ 28
Non-Cash Gain (Loss) on Extinguishment of Debt	$ (5)
6.250% Senior Notes due 2026
Debt Instrument [Line Items]
Interest rate	6.25%			6.25%
Debt Extinguished	$ 370	$ 18	$ 32
2025 Senior Notes
Debt Instrument [Line Items]
Interest rate	6.875%			6.875%
Debt Extinguished	$ 718	$ 14	18
2029 Senior Secured Notes
Debt Instrument [Line Items]
Interest rate	6.625%			6.625%	6.625%
Debt Extinguished	$ 180
2025 Senior Secured Notes
Debt Instrument [Line Items]
Interest rate	12.00%			12.00%
Debt Extinguished			1,056
Cash Gain (Loss) on Extinguishment of Debt			181
Non-Cash Gain (Loss) on Extinguishment of Debt			71
Export-Import Credit Agreement
Debt Instrument [Line Items]
Debt Extinguished			180
Non-Cash Gain (Loss) on Extinguishment of Debt			$ 3

Debt - Debt Redemption Percenta

Debt - Debt Redemption Percentages (Details)	Feb. 11, 2021	Sep. 18, 2020	Sep. 10, 2020	May 31, 2019
2029 Senior Notes | Period One | Condition 1
Debt Instrument, Redemption [Line Items]
Redemption price percentage	100.00%
2029 Senior Notes | Period Two | Condition 1
Debt Instrument, Redemption [Line Items]
Redemption price percentage	103.438%
2029 Senior Notes | Period Three | Condition 1
Debt Instrument, Redemption [Line Items]
Redemption price percentage	101.719%
2029 Senior Notes | Period Four | Condition 1
Debt Instrument, Redemption [Line Items]
Redemption price percentage	100.00%
2029 Senior Secured Notes | Period One | Condition 1
Debt Instrument, Redemption [Line Items]
Redemption price percentage		103.313%
2029 Senior Secured Notes | Period Two | Condition 1
Debt Instrument, Redemption [Line Items]
Redemption price percentage		101.656%
2029 Senior Secured Notes | Period Three | Condition 1
Debt Instrument, Redemption [Line Items]
Redemption price percentage		100.00%
Big River Steel Environmental Revenue Bonds - Series 2019 | Period One | Condition 1
Debt Instrument, Redemption [Line Items]
Redemption price percentage				103.00%
Big River Steel Environmental Revenue Bonds - Series 2019 | Period Two | Condition 1
Debt Instrument, Redemption [Line Items]
Redemption price percentage				102.00%
Big River Steel Environmental Revenue Bonds - Series 2019 | Period Three | Condition 1
Debt Instrument, Redemption [Line Items]
Redemption price percentage				101.00%
Big River Steel Environmental Revenue Bonds - Series 2019 | Period Four | Condition 1
Debt Instrument, Redemption [Line Items]
Redemption price percentage				100.00%
Big River Steel Environmental Revenue Bonds - Series 2020
Debt Instrument, Redemption [Line Items]
Redemption price percentage			100.00%
Big River Steel Environmental Revenue Bonds - Series 2020 | Period One | Condition 1
Debt Instrument, Redemption [Line Items]
Redemption price percentage			103.00%
Big River Steel Environmental Revenue Bonds - Series 2020 | Period Two | Condition 1
Debt Instrument, Redemption [Line Items]
Redemption price percentage			102.00%
Big River Steel Environmental Revenue Bonds - Series 2020 | Period Three | Condition 1
Debt Instrument, Redemption [Line Items]
Redemption price percentage			101.00%
Big River Steel Environmental Revenue Bonds - Series 2020 | Period Four | Condition 1
Debt Instrument, Redemption [Line Items]
Redemption price percentage			100.00%

Debt - Narrative (Details)

Debt - Narrative (Details)

Feb. 11, 2021USD ($)

Sep. 18, 2020USD ($)

Sep. 10, 2020USD ($)

May 31, 2019USD ($)

Sep. 30, 2021USD ($)

Sep. 30, 2020USD ($)

Sep. 30, 2021EUR (€)

Sep. 29, 2021USD ($)

Sep. 29, 2021EUR (€)

Sep. 28, 2021EUR (€)

Jul. 23, 2021USD ($)

Jul. 22, 2021USD ($)

Dec. 31, 2019agreement

Aug. 23, 2017USD ($)

Debt Instrument [Line Items]

Repayment of debt

$ 2,719,000,000

$ 8,000,000

2029 Senior Notes

Debt Instrument [Line Items]

Aggregate principal amount

$ 750,000,000

Interest rate

6.875%

6.875%

6.875%

Proceeds from issuance of senior long-term debt

$ 739,000,000

Fees related to underwriting and third party expenses

$ 11,000,000

2029 Senior Notes | Condition 1 | Period One

Debt Instrument [Line Items]

Redemption price percentage

100.00%

Basis rate

0.50%

2029 Senior Notes | Condition 1 | Minimum

Debt Instrument [Line Items]

Notice period

15 days

2029 Senior Notes | Condition 1 | Maximum

Debt Instrument [Line Items]

Notice period

60 days

2029 Senior Notes | Condition 2 | Period One

Debt Instrument [Line Items]

Redemption price percentage

106.875%

Percentage of principal amount

35.00%

2029 Senior Secured Notes

Debt Instrument [Line Items]

Aggregate principal amount

$ 900,000,000

Interest rate

6.625%

6.625%

6.625%

2029 Senior Secured Notes | Senior Notes

Debt Instrument [Line Items]

Redemption price percentage

103.00%

Maximum amount of principal that can be redeemed

$ 90,000,000

2029 Senior Secured Notes | Condition 1 | Period One

Debt Instrument [Line Items]

Redemption price percentage

103.313%

2029 Senior Secured Notes | Condition 2

Debt Instrument [Line Items]

Redemption price percentage

100.00%

Big River Steel Environmental Revenue Bonds - Series 2019

Debt Instrument [Line Items]

Aggregate principal amount

$ 487,000,000

Interest rate

4.50%

Big River Steel Environmental Revenue Bonds - Series 2019 | Big River Steel LLC

Debt Instrument [Line Items]

Percent of proceeds loaned to third-party

100.00%

Big River Steel Environmental Revenue Bonds - Series 2019 | Condition 1 | Period One

Debt Instrument [Line Items]

Redemption price percentage

103.00%

Big River Steel Environmental Revenue Bonds - Series 2019 | Condition 2 | Period One

Debt Instrument [Line Items]

Redemption price percentage

100.00%

Big River Steel Environmental Revenue Bonds - Series 2020

Debt Instrument [Line Items]

Aggregate principal amount

$ 265,000,000

Interest rate

4.75%

Redemption price percentage

100.00%

Big River Steel Environmental Revenue Bonds - Series 2020 | Big River Steel LLC

Debt Instrument [Line Items]

Percent of proceeds loaned to third-party

100.00%

Big River Steel Environmental Revenue Bonds - Series 2020 | Condition 1 | Period One

Debt Instrument [Line Items]

Redemption price percentage

103.00%

Arkansas Teacher Retirement System Notes Payable

Debt Instrument [Line Items]

Number of agreements | agreement

3

Notes payable

$ 106,000,000

Arkansas Teacher Retirement System Notes Payable | Minimum

Debt Instrument [Line Items]

Interest rate

5.50%

5.50%

5.50%

Arkansas Teacher Retirement System Notes Payable | Maximum

Debt Instrument [Line Items]

Interest rate

7.75%

7.75%

7.75%

Big River Steel ABL Facility | Revolving Credit Facility

Debt Instrument [Line Items]

Debt instrument, term

5 years

Maximum borrowing capacity on credit facility

$ 350,000,000

Amount outstanding

$ 0

Current borrowing capacity

350,000,000

Fixed charge coverage ratio, minimum

1

Fixed charge coverage ratio, maximum

1

Threshold percentage of borrowing base

10.00%

Threshold amount

$ 13,000,000

Credit Facility Agreement

Debt Instrument [Line Items]

Maximum borrowing capacity on credit facility

$ 1,750,000,000

$ 2,000,000,000

Letters of credit outstanding

4,000,000

Available borrowing capacity

$ 1,746,000,000

Credit Facility Agreement | Covenant Requirement

Debt Instrument [Line Items]

Fixed charge coverage ratio, minimum

1

1

Fixed charge coverage ratio, maximum

1

1

Percentage of total aggregate commitments, upper range under financial covenant

10.00%

10.00%

Credit Agreement, upper range of outstanding debt

$ 175,000,000

USSK Credit Agreement | Revolving Credit Facility

Debt Instrument [Line Items]

Debt instrument, term

5 years

Maximum borrowing capacity on credit facility

$ 347,000,000

€ 300,000,000

€ 460,000,000

USSK €20 Million Unsecured Credit Facility | Revolving Credit Facility

Debt Instrument [Line Items]

Maximum borrowing capacity on credit facility | €

€ 20,000,000

USSK Credit Facility | Revolving Credit Facility

Debt Instrument [Line Items]

Maximum borrowing capacity on credit facility

$ 23,000,000

Available borrowing capacity

17,000,000

Customs and other guarantees outstanding

$ 6,000,000

Fair Value of Financial Instr_3

Fair Value of Financial Instruments - Financial Assets and Liabilities Not Carried at Fair Value (Detail) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Fair Value
Financial liabilities:
Short-term and long-term debt (a)	$ 4,663	$ 5,323
Carrying Amount
Financial liabilities:
Short-term and long-term debt (a)	$ 3,996	$ 4,806

Fair Value of Financial Instr_4

Fair Value of Financial Instruments - Additional Information (Details) $ in Millions	Apr. 30, 2020USD ($)installment	Oct. 31, 2019	Sep. 30, 2020USD ($)	Dec. 08, 2020USD ($)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Net change in fair value of options			$ 40
Big River Steel
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Business Combination, Contingent Consideration, Asset				$ 11
Big River Steel
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity Method Investment, Ownership Percentage		49.90%
Equity Method Investment, Remaining Ownership Percentage, Call Period		4 years
Stelco [Member] | Minntac Mine
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest offered in option	25.00%
Aggregate consideration for option	$ 100
Number of installment payments | installment	5
Consideration per installment	$ 20
Additional contribution to Joint Venture upon exercise	$ 500

Statement of Changes in Stock_3

Statement of Changes in Stockholders' Equity (Detail) - USD ($) $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of year	$ 5,943	$ 4,720	$ 3,879	$ 3,654	$ 3,726	$ 4,093	$ 3,879	$ 4,093
Comprehensive income (loss):
Net earnings (loss)	2,002	1,012	91	(234)	(589)	(391)	3,105	(1,214)
Other comprehensive income (loss), net of tax:
Pension and other benefit adjustments	15	205	24	16	29	52	244	97
Currency translation adjustment	(26)	23	(47)	34	20	(23)	(50)	31
Derivative financial instruments	60	(31)	(20)	8	15	(5)
Employee stock plans	16	17	6	10	8	2
Common Stock Issued			790		410
Dividends paid on common stock	(3)	(2)	(3)	(3)	(1)	(2)
Stelco Option Agreement				18	37
Other	1	(1)		1	(1)
Ending balance	8,008	5,943	4,720	3,504	3,654	3,726	8,008	3,504
(Accumulated Deficit) Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of year	480	(532)	(623)	(438)	151	544	(623)	544
Comprehensive income (loss):
Net earnings (loss)	2,002	1,012	91	(234)	(589)	(391)
Other comprehensive income (loss), net of tax:
Dividends paid on common stock	(3)	0	0	0	0	(2)
Other	1			1
Ending balance	2,480	480	(532)	(671)	(438)	151	2,480	(671)
Accumulated Other Comprehensive (Loss) Income
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of year	107	(90)	(47)	(390)	(454)	(478)	(47)	(478)
Other comprehensive income (loss), net of tax:
Pension and other benefit adjustments	15	205	24	16	29	52
Currency translation adjustment	(26)	23	(47)	34	20	(23)
Derivative financial instruments	60	(31)	(20)	8	15	(5)
Ending balance	156	107	(90)	(332)	(390)	(454)	156	(332)
Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of year	279	279	229	229	179	179	229	179
Other comprehensive income (loss), net of tax:
Employee stock plans		0	2	0	0	0
Common Stock Issued			48		50
Ending balance	279	279	279	229	229	179	279	229
Treasury Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of year	(183)	(182)	(175)	(175)	(175)	(173)	(175)	(173)
Other comprehensive income (loss), net of tax:
Employee stock plans	(1)	(1)	(7)	0	0	(2)
Ending balance	(184)	(183)	(182)	(175)	(175)	(175)	(184)	(175)
Paid-in Capital
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of year	5,168	5,152	4,402	4,391	4,024	4,020	4,402	4,020
Other comprehensive income (loss), net of tax:
Employee stock plans	17	18	11	10	8	4
Common Stock Issued			742		360
Dividends paid on common stock	0	(2)	(3)	(3)	(1)
Ending balance	5,185	5,168	5,152	4,398	4,391	4,024	5,185	4,398
Non- Controlling Interest
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of year	92	93	93	37	1	1	93	1
Other comprehensive income (loss), net of tax:
Stelco Option Agreement				18	37
Other		(1)			(1)
Ending balance	$ 92	$ 92	$ 93	$ 55	$ 37	$ 1	$ 92	$ 55

Reclassifications from Accumu_3

Reclassifications from Accumulated Other Comprehensive Income (AOCI) - Other Comprehensive Income Activity Net of Tax (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance			$ (47)	$ (478)
Other comprehensive income (loss) before reclassifications			91	31
Amounts reclassified from AOCI			112	115
Total other comprehensive income, net of tax	$ 49	$ 58	203	146
Ending Balance	156	(332)	156	(332)
Pension and Other Benefit Items
Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance			(458)	(843)
Other comprehensive income (loss) before reclassifications			190	6
Amounts reclassified from AOCI			54	91
Total other comprehensive income, net of tax			244	97
Ending Balance	(214)	(746)	(214)	(746)
Foreign Currency Items
Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance			449	381
Other comprehensive income (loss) before reclassifications			(50)	31
Amounts reclassified from AOCI			0	0
Total other comprehensive income, net of tax			(50)	31
Ending Balance	399	412	399	412
Unrealized (Loss) Gain on Derivatives
Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance			(38)	(16)
Other comprehensive income (loss) before reclassifications			(49)	(6)
Amounts reclassified from AOCI			58	24
Total other comprehensive income, net of tax			9	18
Ending Balance	$ (29)	$ 2	$ (29)	$ 2

Reclassifications from Accumu_4

Reclassifications from Accumulated Other Comprehensive Income (AOCI) - Defined Benefit Plan In Other Comprehensive Income (Detail) - USD ($) $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Amortization of pension and other benefit items
Derivative reclassifications to Condensed Consolidated Statements of Operations	$ (60)	$ 31	$ 20	$ (8)	$ (15)	$ 5
Total before tax	2,262			(258)			$ 3,329	$ (1,262)
Tax provision	(260)			24			(224)	48
Net of tax	2,002	$ 1,012	$ 91	(234)	$ (589)	$ (391)	3,105	(1,214)
Amount reclassified from AOCI (a)
Amortization of pension and other benefit items
Total before tax	61			39			149	145
Tax provision	(15)			(15)			(37)	(30)
Net of tax	46			24			112	115
Pension and Other Benefit Items | Amount reclassified from AOCI (a)
Amortization of pension and other benefit items
Prior service credits (a)	(7)			(1)			(20)	(4)
Actuarial losses (a)	23			32			86	96
Settlement, termination and curtailment losses (a)	5			2			6	2
UPI Purchase Accounting Adjustment	0			0			0	23
Total pensions and other benefits items	21			33			72	117
Unrealized (Loss) Gain on Derivatives | Amount reclassified from AOCI (a)
Amortization of pension and other benefit items
Derivative reclassifications to Condensed Consolidated Statements of Operations	$ 40			$ 6			$ 77	$ 28

Transactions with Related Par_2

Transactions with Related Parties - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Related Party Transaction [Line Items]
Net sales to related parties	$ 341	$ 268	$ 977	$ 710
Accounts payable to related parties	130		130		$ 105
PRO-TEC Coating Company
Related Party Transaction [Line Items]
Accounts payable to related parties	128		128		86
Other equity investees
Related Party Transaction [Line Items]
Accounts payable to related parties	2		2		$ 19
Outside processing services
Related Party Transaction [Line Items]
Purchases from related parties	6	9	32	47
Taconite pellets
Related Party Transaction [Line Items]
Purchases from related parties	$ 26	$ 19	$ 80	$ 53

Restructuring and Other Charg_3

Restructuring and Other Charges - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Restructuring Cost and Reserve [Line Items]
Additional charges	$ 0	$ 0	$ 37	$ 130
Cash payments for restructuring			62
Great Lakes Works
Restructuring Cost and Reserve [Line Items]
Additional charges			27
Environmental and Other Charges
Restructuring Cost and Reserve [Line Items]
Additional charges			10
Business Exit and Employee Severance
Restructuring Cost and Reserve [Line Items]
Additional charges				130
Cash payments for restructuring	$ 9		$ 53
Business Exit and Employee Severance | Postretirement Benefit Trust (VEBA)
Restructuring Cost and Reserve [Line Items]
Cash payments for restructuring				29
Idling of Keetac Mining Operations and Portion of Great Lake Works
Restructuring Cost and Reserve [Line Items]
Additional charges				72
Idling of Lorain Tubular Operations and Lone Star Tubular Operations
Restructuring Cost and Reserve [Line Items]
Additional charges				13
Employee benefit costs
Restructuring Cost and Reserve [Line Items]
Additional charges				13
Reductions under Voluntary Early Retirement Program (VERP)
Restructuring Cost and Reserve [Line Items]
Additional charges				$ 32

Restructuring and Other Charg_4

Restructuring and Other Charges - Schedule of Accrued Balances From Restructuring and Other Charges (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Restructuring Reserve [Roll Forward]
Balance at December 31, 2020			$ 177
Additional charges	$ 0	$ 0	37	$ 130
Cash payments/utilization (a)			(62)
Balance at September 30, 2021	152		152
Employee Related Costs
Restructuring Reserve [Roll Forward]
Balance at December 31, 2020			51
Additional charges			3
Cash payments/utilization (a)			(35)
Balance at September 30, 2021	19		19
Payments for employee related costs from pension fund trust assets			8
Exit Costs
Restructuring Reserve [Roll Forward]
Balance at December 31, 2020			126
Additional charges			33
Cash payments/utilization (a)			(26)
Balance at September 30, 2021	133		133
Non - Cash Charges
Restructuring Reserve [Roll Forward]
Balance at December 31, 2020			0
Additional charges			1
Cash payments/utilization (a)			(1)
Balance at September 30, 2021	$ 0		$ 0

Restructuring and Other Charg_5

Restructuring and Other Charges - Schedule of Accrued Liabilities for Restructuring on Balance Sheet (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Restructuring Cost and Reserve [Line Items]
Accrued liabilities for restructuring and other reduction programs	$ 152	$ 177
Accounts payable
Restructuring Cost and Reserve [Line Items]
Accrued liabilities for restructuring and other reduction programs	35	34
Payroll and benefits payable
Restructuring Cost and Reserve [Line Items]
Accrued liabilities for restructuring and other reduction programs	6	29
Employee benefits
Restructuring Cost and Reserve [Line Items]
Accrued liabilities for restructuring and other reduction programs	13	22
Deferred credits and other noncurrent liabilities
Restructuring Cost and Reserve [Line Items]
Accrued liabilities for restructuring and other reduction programs	$ 98	$ 92

Contingencies and Commitments -

Contingencies and Commitments - Asbestos Litigation Activity (Details) - Asbestos Matters	9 Months Ended		12 Months Ended
	Sep. 30, 2021LegalMatter	Sep. 30, 2021Claim_Group	Dec. 31, 2020Claim_Group	Dec. 31, 2019Claim_Group	Dec. 31, 2018Claim_Group
Loss Contingency Accrual [Roll Forward]
Opening Number of Claims		2,445	2,390	2,320	3,315
Claims Dismissed, Settled and Resolved (a)		135	240	195	1,285
New Claims		205	295	265	290
Closing Number of Claims	1,545	2,515	2,445	2,390	2,320
Number of claims dismissed					1,000

Contingencies and Commitments_2

Contingencies and Commitments - Changes in Accrued Liabilities for Remediation Activities (Detail) $ in Millions	9 Months Ended
	Sep. 30, 2021USD ($)
Change in Accrued Liabilities for Remediation Activities [Roll Forward]
Beginning of period	$ 146
Accruals for environmental remediation deemed probable and reasonably estimable	1
Obligations settled	(23)
End of period	$ 124

Contingencies and Commitments_3

Contingencies and Commitments - Accrued Liabilities for Remediation Activities Included in Balance Sheet (Detail) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Loss Contingencies [Line Items]
Total	$ 124	$ 146
Accounts payable
Loss Contingencies [Line Items]
Total	41	43
Deferred credits and other noncurrent liabilities
Loss Contingencies [Line Items]
Total	$ 83	$ 103

Contingencies and Commitments_4

Contingencies and Commitments - Payments for Contracts with Remaining Terms in Excess of One Year (Detail) $ in Millions	Sep. 30, 2021USD ($)
Commitments and Contingencies Disclosure [Abstract]
Remainder of 2021	$ 299
2022	1,206
2023	557
2024	325
2025	315
Later Years	903
Total	$ 3,605

Contingencies and Commitments_5

Contingencies and Commitments - Additional Information (Detail) € in Millions, Allowances in Millions

3 Months Ended

9 Months Ended

12 Months Ended

Sep. 30, 2021USD ($)LegalMatter

Sep. 30, 2020USD ($)

Sep. 30, 2021USD ($)LegalMatterPlaintiffAllowances

Sep. 30, 2021EUR (€)LegalMatterPlaintiffAllowances

Sep. 30, 2020USD ($)

Dec. 31, 2020USD ($)PlaintiffClaim_GroupLegalMatter

Sep. 30, 2021

Sep. 30, 2021Claim_Group

Sep. 30, 2021USD ($)

Sep. 30, 2021Project

Dec. 31, 2019Claim_Group

Dec. 31, 2018Claim_Group

Dec. 31, 2017Claim_Group

Loss Contingencies [Line Items]

Accrued liabilities for remediation activities

$ 146,000,000

$ 124,000,000

Accrued liabilities for post-closure site monitoring and other costs

23,000,000

Accrued liability for administrative and legal costs

13,000,000

Number of years of projected administrative and legal costs included in accrual

3 years

3 years

Capital expenditures

$ 14,000,000

$ 8,000,000

Estimated Shortfall in Emissions Allowances | Allowances

3.3

3.3

Cost Of Emission Allowances Pre-Purchased

$ 155,000,000

€ 134

Estimated capital expenditures of complying with BAT over 2017 to 2020 period

160,000,000

€ 138

Financial assurance guarantees, maximum

7,000,000

Residual value of equipment

14,000,000

Residual value liability

0

Restricted cash

$ 133,000,000

100,000,000

Contract commitments to acquire property, plant and equipment

687,000,000

Maximum default payment on termination of agreement

87,000,000

Total payment under take-or-pay contracts

$ 215,000,000

$ 123,000,000

$ 584,000,000

$ 425,000,000

Minimum

Loss Contingencies [Line Items]

Projected percentage remediation costs may exceed accrued liabilities

45.00%

45.00%

Unconditional purchase obligation term

2 years

2 years

Maximum

Loss Contingencies [Line Items]

Projected percentage remediation costs may exceed accrued liabilities

70.00%

70.00%

Unconditional purchase obligation term

15 years

15 years

Asbestos Matters

Loss Contingencies [Line Items]

Active cases brought against U.S. Steel | LegalMatter

925

925

925

855

Number of plaintiffs involved | Plaintiff

2,515

2,515

2,445

Number of claims pending in jurisdictions

1,545

1,545

1,545

2,445

2,515

2,390

2,320

3,315

Percentage of claims pending in jurisdictions

61.00%

Projects with Ongoing Study and Scope Development

Loss Contingencies [Line Items]

Environmental remediation projects | Project

5

Accrued liabilities for remediation activities

24,000,000

Projects with Ongoing Study and Scope Development | Minimum

Loss Contingencies [Line Items]

Environment exit costs, possible additional loss

$ 50,000,000

Projects with Ongoing Study and Scope Development | Maximum

Loss Contingencies [Line Items]

Environment exit costs, possible additional loss

$ 75,000,000

Significant Projects with Defined Scope

Loss Contingencies [Line Items]

Environmental remediation projects | Project

2

Accrued liabilities for remediation activities

43,000,000

Significant Projects with Defined Scope | Minimum

Loss Contingencies [Line Items]

Accrued liabilities for remediation activities

5,000,000

Gary Works, Project with Defined Scope

Loss Contingencies [Line Items]

Accrued liabilities for remediation activities

24,000,000

Geneva Project

Loss Contingencies [Line Items]

Accrued liabilities for remediation activities

19,000,000

Environmental Remediation Other Projects

Loss Contingencies [Line Items]

Environmental remediation projects | Project

3

Accrued liabilities for remediation activities

7,000,000

Environmental Remediation Other Projects | Minimum

Loss Contingencies [Line Items]

Accrued liabilities for remediation activities

1,000,000

Environmental Remediation Other Projects | Maximum

Loss Contingencies [Line Items]

Accrued liabilities for remediation activities

5,000,000

Environmental Remediation Projects Less Than One Million

Loss Contingencies [Line Items]

Accrued liabilities for remediation activities

3,000,000

Environmental Remediation Projects Less Than One Million | Maximum

Loss Contingencies [Line Items]

Accrued liabilities for remediation activities

1,000,000

Surety Bonds

Loss Contingencies [Line Items]

Financial assurance guarantees, maximum

$ 214,000,000

Common Stock Issued - Additiona

Common Stock Issued - Additional Information (Details) - USD ($) shares in Millions, $ in Millions	Jun. 22, 2020	Feb. 28, 2021	Sep. 30, 2021	Sep. 30, 2020
Subsidiary, Sale of Stock [Line Items]
Proceeds from public offering of common stock (Note 22)			$ 790	$ 410
Public Offering
Subsidiary, Sale of Stock [Line Items]
Shares issued (in shares)	50	48.3
Proceeds from public offering of common stock (Note 22)	$ 410	$ 790

Subsequent Events (Details)

Subsequent Events (Details) $ in Millions	Oct. 21, 2021USD ($)agreement	Oct. 15, 2021USD ($)	Oct. 01, 2021USD ($)	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)	Oct. 25, 2021USD ($)
Subsequent Event [Line Items]
Repayment of debt				$ 2,719	$ 8
Subsequent Event
Subsequent Event [Line Items]
Amount of shares authorized to be repurchased						$ 300
6.250% Senior Notes due 2026
Subsequent Event [Line Items]
Interest rate				6.25%
6.250% Senior Notes due 2026 | Subsequent Event
Subsequent Events [Abstract]
Aggregate principal amount			$ 230
Subsequent Event [Line Items]
Interest rate			6.25%
Aggregate principal amount			$ 230
Repayment of debt			$ 237
Redemption price percentage			103.125%
Environmental Revenue Bonds | Subsequent Event
Subsequent Events [Abstract]
Aggregate principal amount		$ 70
Subsequent Event [Line Items]
Aggregate principal amount		70
Repayment of debt		$ 70
Arkansas Teacher Retirement System Notes Payable | Subsequent Event
Subsequent Event [Line Items]
Number of instruments paid | agreement	2
Repayment of debt	$ 20