United States Steel (X) 10-Q 29 Oct 13 2013 Q2 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	9 Months Ended
	Sep. 30, 2013	Oct. 24, 2013
Document Documentand Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	FALSE
Document Period End Date	30-Sep-13
Document Fiscal Year Focus	2013
Document Fiscal Period Focus	Q2
Trading Symbol	X
Entity Registrant Name	UNITED STATES STEEL CORP
Entity Central Index Key	1163302
Current Fiscal Year End Date	-19
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		144,666,868

Consolidated_Statement_Of_Oper

Consolidated Statement Of Operations (USD $)	3 Months Ended		9 Months Ended
In Millions, except Per Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Net sales:
Net sales	$3,856	$4,310	$12,292	$13,838
Net sales to related parties (Note 19)	275	342	863	1,003
Total	4,131	4,652	13,155	14,841
Operating expenses (income):
Cost of sales (excludes items shown below)	3,749	4,318	12,105	13,436
Selling, general and administrative expenses	153	159	449	490
Depreciation, depletion and amortization	173	163	514	490
Income from investees	-26	-48	-31	-116
Impairment of goodwill (Note 5)	1,783	0	1,783	0
Net (gain) loss on disposal of assets (Note 4)	0	-1	0	308
Other expense (income), net	1	-1	6	-9
Total	5,833	4,590	14,826	14,599
(Loss) income from operations	-1,702	62	-1,671	242
Interest expense	61	45	204	160
Interest income	0	-1	-2	-6
Other financial costs	24	1	55	23
Net interest and other financial costs (Note 7)	85	45	257	177
(Loss) income before income taxes and noncontrolling interests	-1,787	17	-1,928	65
Income tax provision (benefit) (Note 9)	4	-27	14	139
Net (loss) income	-1,791	44	-1,942	-74
Less: Net income attributable to noncontrolling interests	0	0	0	0
Net (loss) income attributable to United States Steel Corporation	($1,791)	$44	($1,942)	($74)
Earnings per share attributable to United States Steel Corporation shareholders:
Basic (in dollars per share)	($12.38)	$0.30	($13.44)	($0.51)
Diluted (in dollars per share)	($12.38)	$0.28	($13.44)	($0.51)

Consolidated_Statement_Of_Comp

Consolidated Statement Of Comprehensive Income (Loss) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Statement of Comprehensive Income [Abstract]
Net (loss) income	($1,791)	$44	($1,942)	($74)
Other comprehensive income, net of tax:
Changes in foreign currency translation adjustments	31	60	13	76
Changes in pension and other employee benefit accounts	59	224	197	360
Total other comprehensive income, net of tax	90	284	210	436
Comprehensive (loss) income including noncontrolling interest	-1,701	328	-1,732	362
Comprehensive income attributable to noncontrolling interest	0	0	0	0
Comprehensive (loss) income attributable to United States Steel Corporation	($1,701)	$328	($1,732)	$362

Consolidated_Balance_Sheet

Consolidated Balance Sheet (USD $)	Sep. 30, 2013		Dec. 31, 2012
In Millions, unless otherwise specified
Current assets:
Cash and cash equivalents	$697		$570
Receivables, less allowance of $53 and $55	1,819		1,872
Receivables from related parties (Note 19)	138		218
Inventories (Note 12)	2,480		2,503
Deferred income tax benefits (Note 9)	162		171
Other current assets	58		40
Total current assets	5,354		5,374
Property, plant and equipment	17,031		16,906
Less accumulated depreciation and depletion	10,864		10,498
Total property, plant and equipment, net	6,167		6,408
Investments and long-term receivables, less allowance of $3 in both periods	607		609
Intangibles – net (Note 5)	276		253
Goodwill (Note 5)	4		1,822
Deferred income tax benefits (Note 9)	311		424
Other noncurrent assets	287		327
Total assets	13,006		15,217
Current liabilities:
Accounts payable and other accrued liabilities	1,630		1,722
Accounts payable to related parties (Note 19)	93		78
Bank checks outstanding	56		15
Payroll and benefits payable	965		977
Accrued taxes	140		146
Accrued interest	80		50
Short-term debt and current maturities of long-term debt (Note 14)	322		2
Total current liabilities	3,286		2,990
Long-term debt, less unamortized discount (Note 14)	3,618		3,936
Employee benefits	3,919		4,416
Deferred credits and other noncurrent liabilities	408		397
Total liabilities	11,231		11,739
Contingencies and commitments (Note 20)
Stockholders’ Equity (Note 17):
Common stock (150,925,911 shares issued) (Note 11)	151		151
Treasury stock, at cost (6,267,004 and 6,643,553 shares)	-481		-521
Additional paid-in capital	3,665		3,652
Retained earnings	1,497		3,463
Accumulated other comprehensive loss (Note 18)	-3,058	[1]	-3,268	[1]
Total United States Steel Corporation stockholders’ equity	1,774		3,477
Noncontrolling interests	1		1
Total liabilities and stockholders’ equity	$13,006		$15,217
[1]	All amounts are net of tax. Amounts in parentheses indicate debits.

Consolidated_Balance_Sheet_Par

Consolidated Balance Sheet (Parenthetical) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Millions, except Share data, unless otherwise specified
Statement of Financial Position [Abstract]
Receivables, allowance	$53	$55
Investments and long-term receivables, allowance	$3	$3
Common stock, shares issued	150,925,911	150,925,911
Treasury stock, shares	6,276,004	6,643,553

Consolidated_Statement_Of_Cash

Consolidated Statement Of Cash Flows (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
Operating activities:
Net loss	($1,942)	($74)
Adjustments to reconcile to net cash provided by operating activities:
Depreciation, depletion and amortization	514	490
Impairment of goodwill (Note 5)	1,783	0
Provision for doubtful accounts	-2	-3
Pensions and other postretirement benefits	-143	-112
Deferred income taxes	3	86
Net (gain) loss on disposal of assets (Note 4)	0	308
Currency remeasurement loss (gain)	8	-13
Distributions received, net of equity investees income	-20	-33
Changes in:
Current receivables	137	-86
Inventories	15	168
Current accounts payable and accrued expenses	-34	108
Income taxes receivable/payable	1	27
Bank checks outstanding	40	25
All other, net	61	67
Net cash provided by operating activities	421	958
Investing activities:
Capital expenditures	-328	-536
Acquisition of intangible assets (Note 5)	-12	0
Disposal of assets	0	141
Change in restricted cash, net	39	-67
Investments, net	-8	-4
Net cash used in investing activities	-309	-466
Financing activities:
Revolving credit facilities – borrowings	0	523
Revolving credit facilities – repayments	0	-653
Receivables Purchase Agreement payments	0	-380
Issuance of long-term debt, net of financing costs	575	485
Repayment of long-term debt	-542	-319
Dividends paid	-22	-22
Net cash provided by (used in) financing activities	11	-366
Effect of exchange rate changes on cash	4	2
Net increase in cash and cash equivalents	127	128
Cash and cash equivalents at beginning of year	570	408
Cash and cash equivalents at end of period	$697	$536

Basis_of_Presentation

Basis of Presentation	9 Months Ended
	Sep. 30, 2013
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation
	United States Steel Corporation (U. S. Steel) produces and sells steel mill products, including flat-rolled and tubular products, in North America and Central Europe. Operations in North America also include transportation services (railroad and barge operations) and real estate operations.
	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 financial statements is unaudited but, in the opinion of management, reflects all adjustments necessary for a fair presentation of the results for the periods covered. All such adjustments are of a normal recurring nature unless disclosed otherwise. These 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 accounting principles generally accepted in the United States of America for complete financial statements. Additional information is contained in the United States Steel Corporation Annual Report on Form 10-K for the year ended December 31, 2012 which should be read in conjunction with these financial statements.
	Reclassifications
	Certain reclassifications of prior years’ data have been made to conform to the current year presentation.

New_Accounting_Standards

New Accounting Standards	9 Months Ended
	Sep. 30, 2013
Accounting Policies [Abstract]
New Accounting Standards	New Accounting Standards
	On February 5, 2013, the FASB issued Accounting Standards Update No. 2013-02, Reporting of Amounts Reclassified Out of Accumulated Other Comprehensive Income (ASU 2013-02). ASU 2013-02 requires companies to present information about reclassification adjustments from accumulated other comprehensive income, including the amount of the reclassification and the income statement line items affected by the reclassification. The information must be presented in the financial statements in a single note or on the face of the financial statements. ASU 2013-02 is effective for interim and annual periods beginning after December 15, 2012. U. S. Steel adopted ASU 2013-02 effective January 1, 2013 and has provided the required disclosures in Note 18.
	On July 18, 2013, the FASB issued Accounting Standards Update No. 2013-11, Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss, or a Tax Credit Carryforward Exists (ASU 2013-11). ASU 2013-11 requires the netting of unrecognized tax benefits (UTBs) against a deferred tax asset for a loss or other carryforward that would apply in settlement of the uncertain tax positions. UTBs are required to be netted against all available same-jurisdiction loss or other tax carryforwards that would be utilized, rather than only against carryforwards that are created by the UTBs. ASU 2013-11 is effective for interim and annual periods beginning after December 15, 2013. U. S. Steel early adopted ASU 2013-11 in the second quarter of 2013 on a prospective basis. The adoption did not have a significant impact on U. S. Steel's financial statements.

Segment_Information

Segment Information	9 Months Ended
	Sep. 30, 2013
Segment Reporting [Abstract]
Segment Information	Segment Information
	U. S. Steel has three reportable segments: Flat-rolled Products (Flat-rolled), U. S. Steel Europe (USSE), and Tubular Products (Tubular). The results of several other operating segments that do not constitute reportable segments, which include transportation services and real estate operations, are combined and disclosed in the Other Businesses category. Prior to January 31, 2012, our USSE reportable segment consisted of U. S. Steel Košice (USSK) and U. S. Steel Serbia (USSS). On January 31, 2012, U. S. Steel sold USSS (see Note 4). The USSE segment information subsequent to January 31, 2012 reflects the results of USSK only.
	The chief operating decision maker evaluates performance and determines resource allocations based on a number of factors, the primary measure being income (loss) from operations. Income (loss) from operations for reportable segments and Other Businesses does not include net interest and other financial costs (income), income taxes, postretirement benefit expenses (other than service cost and amortization of prior service cost for active employees) and certain other items that management believes are not indicative of future results. Information on segment assets is not disclosed, as it is not reviewed by the chief operating decision maker.
	The accounting principles applied at the operating segment level in determining income (loss) from operations are generally the same as those applied at the consolidated financial statement level. The transfer value for steel rounds from Flat-rolled to Tubular is based on cost. All other intersegment sales and transfers are accounted for at market-based prices and are eliminated at the corporate consolidation level. Corporate-level selling, general and administrative expenses and costs related to certain former businesses are allocated to the reportable segments and Other Businesses based on measures of activity that management believes are reasonable.
	The results of segment operations for the three months ended September 30, 2013 and 2012 are:
	(In millions) Third Quarter 2013	Customer			Intersegment			Net			Income			Income
		Sales			Sales			Sales			(loss)			(loss)
											from			from
											investees			operations
	Flat-rolled	$	2,731		$	324		$	3,055		$	28		$	82
	USSE	643			1			644			—			(32		)
	Tubular	731			2			733			(1		)	49
	Total reportable segments	4,105			327			4,432			27			99
	Other Businesses	26			32			58			(1		)	14
	Reconciling Items and Eliminations	—			(359		)	(359		)	—			(1,815		)
	Total	$	4,131		$	—		$	4,131		$	26		$	(1,702	)
	Third Quarter 2012
	Flat-rolled	$	3,142		$	415		$	3,557		$	49		$	29
	USSE	696			68			764			—			27
	Tubular	787			3			790			(1		)	102
	Total reportable segments	4,625			486			5,111			48			158
	Other Businesses	27			13			40			—			13
	Reconciling Items and Eliminations	—			(499		)	(499		)	—			(109		)
	Total	$	4,652		$	—		$	4,652		$	48		$	62
	The results of segment operations for the nine months ended September 30, 2013 and 2012 are:
	(In millions) First Nine Months 2013	Customer			Intersegment			Net			Income			Income
		Sales			Sales			Sales			(loss)			(loss)
											from			from
											investees			operations
	Flat-rolled	$	8,710		$	985		$	9,695		$	41		$	18
	USSE	2,204			3			2,207			—			16
	Tubular	2,126			4			2,130			(7		)	158
	Total reportable segments	13,040			992			14,032			34			192
	Other Businesses	115			101			216			(3		)	62
	Reconciling Items and Eliminations	—			(1,093		)	(1,093		)	—			(1,925		)
	Total	$	13,155		$	—		$	13,155		$	31		$	(1,671	)
	First Nine Months 2012
	Flat-rolled	$	9,798		$	1,297		$	11,095		$	122		$	389
	USSE	2,274			143			2,417			—			27
	Tubular	2,604			6			2,610			(4		)	334
	Total reportable segments	14,676			1,446			16,122			118			750
	Other Businesses	165			105			270			(2		)	46
	Reconciling Items and Eliminations	—			(1,551		)	(1,551		)	—			(554		)
	Total	$	14,841		$	—		$	14,841		$	116		$	242
	The following is a schedule of reconciling items to income (loss) from operations:
		Three Months Ended September 30,						Nine Months Ended September 30,
	(In millions)	2013			2012			2013			2012
	Items not allocated to segments:
	Postretirement benefit expense(a)	$	(55	)	$	(74	)	$	(165	)	$	(228	)
	Other items not allocated to segments:
	Impairment of goodwill (Note 5)	$	(1,783	)	—			$	(1,783	)	—
	Supplier contract dispute settlement	23			$	—		23			$	—
	Labor agreement lump sum payments(b)	—			(35		)	—			(35		)
	Net loss on the sale of assets (Note 4)	—			—			—			(310		)
	Property tax settlements	—			—			—			19
	Total other items not allocated to segments	(1,760		)	(35		)	(1,760		)	(326		)
	Total reconciling items	$	(1,815	)	$	(109	)	$	(1,925	)	$	(554	)
	(a) Consists of the net periodic benefit cost elements, other than service cost and amortization of prior service cost for active employees, associated with our pension, retiree health care and life insurance benefit plans.
	(b) Effective September 1, 2012, U. S. Steel and its U. S. Steel Tubular Products, Inc. subsidiary reached new labor agreements (the 2012 Labor Agreements) with the United Steel Workers (USW). The 2012 Labor Agreements provided for a $2,000 lump sum payment for each covered active USW member, which resulted in U. S. Steel recognizing a pretax charge of $35 million in the third quarter of 2012.

Dispositions

Dispositions	9 Months Ended
	Sep. 30, 2013
Discontinued Operations and Disposal Groups [Abstract]
Dispositions	Dispositions
	The net loss on disposal of assets for the first nine months of 2012 primarily relates to the following dispositions:
	U. S. Steel Serbia
	On January 31, 2012, U. S. Steel sold USSS to the Republic of Serbia for a purchase price of one dollar. In addition, USSK received a $40 million payment for certain intercompany balances owed by USSS for raw materials and support services. As a result of this transaction, U. S. Steel recorded a total non-cash pretax charge of $399 million.
	Birmingham Southern Railroad Company
	On February 1, 2012, U. S. Steel completed the sale of the majority of the operating assets of Birmingham Southern Railroad Company and the Port Birmingham Terminal. As a result of the transaction, U. S. Steel recorded a pretax gain of $89 million.

Goodwill_and_Intangible_Assets

Goodwill and Intangible Assets	9 Months Ended
	Sep. 30, 2013
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	Goodwill and Intangible Assets
	The changes in the carrying amount of goodwill by segment for the nine months ended September 30, 2013 are as follows:
		Flat-rolled				USSE				Tubular				Total
		Segment				Segment				Segment
	Balance at December 31, 2012	$	984			$	4			$	834			$	1,822
	Goodwill from acquisitions	—				—				3				$	3
	Impairment	(946		)		—				(837		)		(1,783		)
	Currency translation	(38		)		—				—				(38		)
	Balance at September 30, 2013	$	—			$	4			$	—			$	4
	Goodwill represents the excess of the cost over the fair value of acquired identifiable tangible and intangible assets and liabilities assumed from businesses acquired.
	Goodwill is tested for impairment at the reporting unit level annually in the third quarter and whenever events or circumstances indicate the carrying value may not be recoverable. The evaluation of goodwill impairment involves using either a qualitative or quantitative approach as outlined in Accounting Standards Codification (ASC) Topic 350. U. S. Steel completed its annual goodwill impairment evaluation using the two-step quantitative analysis during the third quarter of 2013. We had two reporting units that included nearly all of our goodwill: our Flat-rolled reporting unit and our Texas Operations reporting unit, which is part of our Tubular operating segment.
	In the first step of the analysis, U. S. Steel compared the estimated fair value of each reporting unit to its carrying value, including goodwill. The fair value of the reporting units was determined based on a weighting of income and market approaches. Since the carrying value of both the Flat-rolled and Texas Operations reporting units exceeded the fair value, U. S. Steel performed the second step of the impairment analysis in order to determine the implied fair value of the reporting units’ goodwill. The implied fair value of goodwill represents the excess of fair value of the reporting unit over the fair value amounts assigned to all of the assets and liabilities of the reporting unit as if it were to be acquired in a business combination and the current fair value of the reporting unit (as calculated in the first step) was the purchase price. Any amount remaining after this allocation represents the implied fair value of goodwill. The implied fair value of the respective reporting units’ goodwill was then compared to the carrying value of the goodwill and any excess of carrying value over the implied fair value represents the non-cash impairment charge. The results of the second step preliminary analysis showed that the implied fair value of goodwill was zero for both reporting units. Therefore, in the third quarter of 2013, U. S. Steel recorded a goodwill impairment charge of $946 million and $837 million for the Flat-rolled and Texas Operations reporting units, respectively. As a result of the goodwill impairment charge, there is no goodwill remaining within the Flat-rolled and Tubular segments, and goodwill remaining on our consolidated balance sheet at September 30, 2013 is $4 million.
	The impairment of the Flat-rolled reporting unit’s goodwill was primarily driven by the valuation effects of the protracted economic recovery and excess global steelmaking capacity. The impairment of the Texas Operations reporting unit’s goodwill was primarily driven by the adverse price and volume effects of an increased supply of welded tubular products in the U.S. market from the continued high level of tubular product imports and announced additional domestic tubular manufacturing capacity. Due to these factors, U. S. Steel decreased the long term estimates of its operating results and cash flows utilized in assessing goodwill for impairment. The valuation of goodwill for the second step of the goodwill impairment analysis is considered a level 3 fair value measurement, which means that the valuation of the assets and liabilities reflect U. S. Steel's own assumptions about the assumptions that market participants would use in pricing the assets and liabilities.
	The valuation methodologies used for the 2013 impairment analysis to determine fair value under step one, with the assistance of a third party valuation specialist in the case of the Texas Operations reporting unit, were a market approach and an income approach.
	For purposes of the income approach, fair value was determined based on the present value of estimated future cash flows, discounted at an appropriate risk-adjusted rate (DCF analysis). U. S. Steel made assumptions about the amount and timing of future expected cash flows, terminal value growth rates and appropriate discount rates. The amount and timing of future cash flows within U. S. Steel’s DCF analysis was based on its most recent operational budgets, long range strategic plans and other estimates including probability weighting of cash flow scenarios. A three percent perpetual growth rate was used to calculate the value of cash flows beyond the last projected period in U. S. Steel’s DCF analysis and reflects its best estimates for stable, perpetual growth of its reporting units. Actual results may differ from those assumed in U. S. Steel’s forecasts. U. S. Steel used estimates of market participant weighted average cost of capital (WACC) as a basis for determining the discount rates applied to its reporting units’ future expected cash flows, adjusted for risks and uncertainties inherent in the steel industry and in its internally developed forecasts. A discount rate of 10 percent was used for both reporting units.
	The market approach is based upon an analysis of valuation metrics for companies comparable to each reporting unit. Fair values for the Flat-rolled and Texas Operations reporting units were estimated using an appropriate valuation multiple, as well as estimated normalized earnings and an estimated control premium.
	In order to validate the reasonableness of the estimated fair values of the reporting units as of the valuation date, a reconciliation of the aggregate fair values of all reporting units to market capitalization was performed using a reasonable control premium. We further validated the reasonableness of the estimated fair values of our reporting units using other valuation metrics that included data from U. S Steel's historical transactions as well as published industry analyst reports.
	Goodwill impairment tests in prior years indicated that goodwill was not impaired for any of U. S. Steel's reporting units and there were no triggering events since that time that necessitated an impairment test.
	Amortizable intangible assets are being amortized on a straight-line basis over their estimated useful lives and are detailed below:
				As of September 30, 2013												As of December 31, 2012
	(In millions)	Useful		Gross				Accumulated				Net				Gross		Accumulated		Net
		Lives		Carrying				Amortization				Amount				Carrying		Amortization		Amount
				Amount												Amount
	Customer relationships	22-23 Years		$	218			$	61			$	157			$	221	$	54	$	167
	Other	2-20 Years		23				12				11				22		11		11
	Total amortizable intangible assets			$	241			$	73			$	168			$	243	$	65	$	178
	The carrying amount of acquired water rights with indefinite lives as of September 30, 2013 and December 31, 2012 totaled $75 million. The water rights are tested for impairment annually in the third quarter. U. S. Steel performed a qualitative impairment evaluation of its water rights for 2013. The 2013 and prior year tests indicated the water rights were not impaired.
	During the first nine months of 2013, U. S. Steel acquired indefinite-lived intangible assets for $12 million and entered into an agreement to make future payments contingent upon certain factors. The aggregate purchase price was $36 million, and U. S. Steel allocated $33 million to indefinite-lived intangible assets, based upon their estimated fair value. The liability for contingent consideration will be reassessed each quarter. The maximum potential liability for contingent consideration is $53 million. As of September 30, 2013, U. S. Steel has recorded a liability of $24 million to reflect the estimated fair value of the contingent consideration. Contingent consideration was valued using a probability weighted discounted cash flow using both level 2 inputs based on 2013 Standard and Poor’s Bond Guide as well level 3, significant other unobservable inputs, based on internal forecasts and weighted average cost of capital derived from market data.
	Identifiable intangible assets with finite lives are reviewed for impairment whenever events or circumstances indicate that the carrying value may not be recoverable. During the third quarter of 2013, U. S. Steel completed a review of its identifiable intangible assets with finite lives and determined that the assets were not impaired.
	Amortization expense was $3 million in both the three months ended September 30, 2013 and 2012 and was $8 million in both the nine months ended September 30, 2013 and 2012. The estimated future amortization expense of identifiable intangible assets during the next five years is $3 million for the remaining portion of 2013 and $11 million each year from 2014 to 2017.

Pensions_and_Other_Benefits

Pensions and Other Benefits	9 Months Ended
	Sep. 30, 2013
Compensation and Retirement Disclosure [Abstract]
Pensions and Other Benefits	Pensions and Other Benefits
	The following table reflects the components of net periodic benefit cost for the three months ended September 30, 2013 and 2012:
		Pension						Other
		Benefits						Benefits
	(In millions)	2013			2012			2013			2012
	Service cost	$	32		$	29		$	7		$	7
	Interest cost	100			117			35			42
	Expected return on plan assets	(152		)	(154		)	(33		)	(29		)
	Amortization of prior service cost	6			6			(3		)	3
	Amortization of actuarial net loss	92			88			8			1
	Net periodic benefit cost, excluding below	78			86			14			24
	Multiemployer plans	19			18			—			—
	Settlement, termination and curtailment losses	$	3		$	—		$	—		$	—
	Net periodic benefit cost	$	100		$	104		$	14		$	24
	The following table reflects the components of net periodic benefit cost for the nine months ended September 30, 2013 and 2012:
		Pension						Other
		Benefits						Benefits
	(In millions)	2013			2012			2013			2012
	Service cost	$	96		$	88		$	21		$	22
	Interest cost	303			350			106			133
	Expected return on plan assets	(459		)	(460		)	(98		)	(86		)
	Amortization of prior service cost	18			15			(10		)	14
	Amortization of actuarial net loss	275			264			23			1
	Net periodic benefit cost, excluding below	233			257			42			84
	Multiemployer plans	55			52			—			—
	Settlement, termination and curtailment losses (gains)	3			(2		)	—			—
	Net periodic benefit cost	$	291		$	307		$	42		$	84
	Employer Contributions
	During the first nine months of 2013, U. S. Steel made a voluntary contribution of $140 million to its main defined benefit pension plan. U. S. Steel also made $63 million in required cash contributions to the USSC pension plans, cash payments of $56 million to the Steelworkers’ Pension Trust and $18 million of pension payments not funded by trusts.
	During the first nine months of 2013, cash payments of $188 million were made for other postretirement benefit payments not funded by trusts. In addition, U. S. Steel made a required contribution of $10 million to our trust for represented retiree health care and life insurance benefits.
	Company contributions to defined contribution plans totaled $11 million and $10 million in the three months ended September 30, 2013 and 2012, respectively. Company contributions to defined contribution plans totaled $33 million and $31 million for the nine months ended September 30, 2013 and 2012, respectively.
	Pension Funding
	In January 2013, U. S. Steel's Board of Directors authorized voluntary contributions to U. S. Steel's trusts for pensions and other benefits of up to $300 million through the end of 2014. U. S. Steel made voluntary contributions to our main U.S. defined benefit plan of $140 million during the first nine months of 2013 and 2012. U. S. Steel will likely make voluntary contributions of similar amounts in future periods in order to mitigate potentially larger mandatory contributions in later years. Assuming future asset performance consistent with our expected long-term earnings rate assumption of 7.75%, we anticipate that the interest rate formula changes in the pension stabilization legislation enacted in 2012 will allow us to continue to make voluntary contributions of approximately $140 million per year through 2015 to our main U.S. defined benefit plan before we could be required to contribute more than that amount should the current low interest rate environment continue.

Net_Interest_and_Other_Financi

Net Interest and Other Financial Costs	9 Months Ended
	Sep. 30, 2013
Debt Disclosure [Abstract]
Net Interest and Other Financial Costs	Net Interest and Other Financial Costs
	Net interest and other financial costs includes interest expense (net of capitalized interest), interest income, financing costs, derivatives gains and losses and foreign currency remeasurement gains and losses. Foreign currency gains and losses are a result of foreign currency denominated assets and liabilities that require remeasurement. During the three months ended September 30, 2013 and 2012, net foreign currency remeasurement gains of $3 million and $6 million, respectively, were recorded in other financial costs. During the nine months ended September 30, 2013 and 2012, net foreign currency remeasurement losses of $9 million and $2 million, respectively, were recorded in other financial costs.
	For the three and nine months ended September 30, 2013, net interest and other financial costs includes a charge of $22 million related to a guarantee of an unconsolidated equity investment for which payment by U. S. Steel is probable (see Note 20). Also included in the nine months ended September 30, 2013 is a charge of $34 million related to repurchases of approximately $542 million aggregate principal amount of our 4.00% Senior Convertible Notes due May 15, 2014 (see Note 14 for further details). For the nine months ended September 30, 2012, net interest and other financial costs also includes a charge of $18 million associated with the April 2012 redemption of all of our $300 million Senior Notes due June 1, 2013.
	See Note 13 for additional information on U. S. Steel’s use of derivatives to mitigate its foreign currency exchange rate exposure.

StockBased_Compensation_Plans

Stock-Based Compensation Plans	9 Months Ended
	Sep. 30, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation Plans	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 (the Committee) under several stock-based employee compensation plans, which are more fully described in Note 12 of the United States Steel Corporation 2012 Annual Report on Form 10-K. An aggregate of 15,450,000 shares of U. S. Steel common stock may be issued under the plans. As of September 30, 2013, 1,325,239 shares are available for future grants.
	U. S. Steel recognized pre-tax stock-based compensation cost in the amount of $9 million and $10 million in the three months ended September 30, 2013 and 2012, respectively, and $28 million and $29 million in the first nine months of 2013 and 2012, respectively.
	Recent grants of stock-based compensation consist of stock options, restricted stock units and performance awards. Historically, the Committee has granted traditional stock options with an exercise price equal to the stock price on the date of grant. For the 2013 grants, premium-priced stock options with an exercise price of $25 per share were awarded to executives in lieu of traditional stock options. The following table is a general summary of the awards made under the Plan.
		2013 Grants					2012 Grants
	Grant Details	Shares (a)		Fair Value (b)			Shares (a)		Fair Value (b)
	Executive Stock Options	826,340		$	8.37		510,570		$	11.93
	Non-executive Stock Options	970,640		$	9.7		993,310		$	11.93
	Restricted Stock Units	1,033,210		$	18.58		910,011		$	22.28
	Performance Awards (c)	271,960		$	21.26		328,780		$	25.26
	(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 year.
	(c) The number of Performance Awards shown represents the target value of the award.
	As of September 30, 2013, total future compensation cost related to nonvested stock-based compensation arrangements was $50 million, and the weighted average period over which this cost is expected to be recognized is approximately 1.3 years.
	Compensation expense for stock options is recorded over the vesting period based on the fair value on the date of grant, as calculated by U. S. Steel using the Black-Scholes model and the assumptions listed below. The stock options vest ratably over a three-year service period and have a term of ten years.
	Black-Scholes Assumptions(a)		2013 Executive Grants			2013 Non-Executive Grants				2012 Grants
	Grant date price per share of option award		$	18.48		$	18.64			$	22.28
	Exercise price per share of option award		$	25		$	18.64			$	22.28
	Expected annual dividends per share, at grant date		$	0.2		$	0.2			$	0.2
	Expected life in years		5			5				5
	Expected volatility		66		%	67		%		68		%
	Risk-free interest rate		1.315		%	1.049		%		0.8		%
	Grant date fair value per share of unvested option awards as calculated from above		$	8.37		$	9.7			$	11.93
	(a) The assumptions represent a weighted average of all grants during the year.
	The expected annual dividends per share are based on the latest annualized dividend rate at the date of grant; the expected life in years is determined primarily from historical stock option exercise data; the expected volatility is based on the historical volatility of U. S. Steel stock; and the risk-free interest rate is based on the U.S. Treasury strip rate for the expected life of the option.
	Restricted stock units generally vest ratably over three years. The fair value of the restricted stock units is the market price of the underlying common stock on the date of the grant.
	Performance awards vest at the end of a three-year performance period as a function of U. S. Steel's total shareholder return compared to the total shareholder return of a group of peer companies over the three-year performance period. Performance awards can vest at between zero and 200 percent of the target award. The fair value of the performance awards is calculated using a Monte-Carlo simulation.

Income_Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2013
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes
	Tax provision
	For the nine months ended September 30, 2013 and 2012, we recorded a tax provision of $14 million on our pretax loss of $1.9 billion and a tax provision of $139 million on our pretax income of $65 million, respectively. The tax provision does not reflect any tax benefit for pretax losses in Canada and Serbia (USSS was sold on January 31, 2012), which are jurisdictions where we have, or had, recorded full valuation allowances on deferred tax assets, and also does not reflect any tax provision or benefit for certain foreign currency remeasurement gains and losses that are not recognized in any tax jurisdiction. For the nine months ended September 30, 2013, there was essentially no tax benefit recorded on the $1.8 billion goodwill impairment charge. For the nine months ended September 30, 2012, no significant tax benefit was recorded on the $399 million loss on the sale of USSS.
	The tax provision for the first nine months of 2013 is based on an estimated annual effective rate, which requires management to make its best estimate of annual pretax income or loss. During 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 2013 pretax results for U.S. and foreign income or loss vary from estimates applied herein, the actual tax provision or benefit recognized in 2013 could be materially different from the forecasted amount used to estimate the tax provision for the nine months ended September 30, 2013.
	Unrecognized tax benefits
	Unrecognized tax benefits are the differences between a tax position taken, or expected to be taken, in a tax return and the benefit recognized for accounting purposes pursuant to the guidance in ASC Topic 740 on income taxes. The total amount of gross unrecognized tax benefits was $85 million at both September 30, 2013 and December 31, 2012. The total amount of net unrecognized tax benefits that, if recognized, would affect the effective tax rate was $65 million as of both September 30, 2013 and December 31, 2012.
	U. S. Steel records interest related to uncertain tax positions as a part of net interest and other financial costs in the Consolidated Statement of Operations. Any penalties are recognized as part of selling, general and administrative expenses. As of both September 30, 2013 and December 31, 2012, U. S. Steel had accrued liabilities of $7 million for interest related to uncertain tax positions. U. S. Steel currently does not have a liability for tax penalties.
	It is reasonably expected that during the next 12 months unrecognized tax benefits related to income tax issues will decrease by approximately $8 million.
	Deferred taxes
	As of September 30, 2013, the net domestic deferred tax asset was $411 million compared to $538 million at December 31, 2012. A substantial amount of U. S. Steel’s domestic deferred tax assets relates to employee benefits that will become deductible for tax purposes over an extended period of time as cash contributions are made to employee benefit plans and retiree benefits are paid in the future. We continue to believe it is more likely than not that the net domestic deferred tax asset will be realized.
	As of September 30, 2013, the net foreign deferred tax asset was $62 million, net of established valuation allowances of $1,184 million. At December 31, 2012, the net foreign deferred tax asset was $57 million, net of established valuation allowances of $1,099 million. The net foreign deferred tax asset will fluctuate as the value of the U.S. dollar changes with respect to the euro and the Canadian dollar. At December 31, 2012, a full valuation allowance was recorded for the net Canadian deferred tax asset primarily due to cumulative losses in Canada in recent years.
	If evidence changes and it becomes more likely than not that the Company will realize the net Canadian deferred tax asset, the valuation allowance would be partially or fully reversed. Any reversal of this amount would result in a decrease to income tax expense. The Slovak income tax rate increased from 19% to 23% starting in 2013. This change had an insignificant impact on deferred taxes at the end of 2012.

Significant_Equity_Investments

Significant Equity Investments	9 Months Ended
	Sep. 30, 2013
Equity Method Investments and Joint Ventures [Abstract]
Significant Equity Investments	Significant Equity Investments
	Summarized unaudited income statement information for our significant equity investments for the nine months ended September 30, 2013 and 2012 is reported below (amounts represent 100% of investee financial information):
	(In millions)	2013		2012
	Net sales	$	1,841	$	1,982
	Cost of sales	1,395		1,421
	Operating income	399		533
	Net income	382		521
	Net income attributable to significant equity investments	382		521
	U. S. Steel’s portion of the equity in net income of the significant equity investments above was $50 million and $121 million for the nine months ended September 30, 2013 and 2012, respectively, which is included in the income from investees line on the Consolidated Statement of Operations.

Earnings_and_Dividends_Per_Com

Earnings and Dividends Per Common Share	9 Months Ended
	Sep. 30, 2013
Earnings Per Share [Abstract]
Earnings and Dividends Per Common Share	Earnings and Dividends Per Common Share
	Earnings Per Share Attributable to United States Steel Corporation Shareholders
	Basic earnings per common share is based on the weighted average number of common shares outstanding during the period.
	Diluted earnings per common share assumes the exercise of stock options, the vesting of restricted stock units and performance awards and the conversion of convertible notes, provided in each case the effect is dilutive. The “if-converted” method is used to calculate the dilutive effect of the Senior Convertible Notes due in 2014 and the “treasury stock” method is used to calculate the dilutive effect of the Senior Convertible Notes due in 2019 (due to our current intent and policy, among other factors, to settle the principal amount of the 2019 Senior Convertible Notes in cash upon conversion).
	The computations for basic and diluted earnings per common share from continuing operations are as follows:
		Three Months Ended September 30,							Nine Months Ended September 30,
	(Dollars in millions, except per share amounts)	2013				2012			2013			2012
	Net (loss) income attributable to United States Steel
	Corporation shareholders	$	(1,791	)		$	44		$	(1,942	)	$	(74	)
	Plus income effect of assumed conversion-interest on convertible notes	—				5			—			—
	Net (loss) income after assumed conversion	$	(1,791	)		$	49		$	(1,942	)	$	(74	)
	Weighted-average shares outstanding (in thousands):
	Basic	144,727				144,350			144,523			144,199
	Effect of convertible notes	—				27,059			—			—
	Effect of stock options, restricted stock units and performance awards	—				264			—			—
	Adjusted weighted-average shares outstanding, diluted	144,727				171,673			144,523			144,199
	Basic earnings per common share	$	(12.38	)		$	0.3		$	(13.44	)	$	(0.51	)
	Diluted earnings per common share	$	(12.38	)		$	0.28		$	(13.44	)	$	(0.51	)
	The following table summarizes the securities that were antidilutive, and therefore, were not included in the computations of diluted earnings per common share:
		Three Months Ended September 30,						Nine Months Ended September 30,
	(In thousands)	2013			2012			2013		2012
	Securities granted under the 2005 Stock Incentive Plan	7,621			4,352			7,621		4,353
	Securities convertible under the Senior Convertible Notes	10,058			—			15,351	(a)	27,059
	Total	17,679			4,352			22,972		31,412
	(a) On March 27, 2013, we repurchased approximately $542 million aggregate principal amount of our 4% Senior Convertible Notes due in 2014. If the repurchases had occurred on January 1, 2013, the antidilutive securities would be 10,058 for the nine months ended September 30, 2013.
	Dividends Paid Per Share
	The dividend for each of the first three quarters of 2013 and 2012 was five cents per common share.

Inventories

Inventories	9 Months Ended
	Sep. 30, 2013
Inventory Disclosure [Abstract]
Inventories	Inventories
	Inventories are carried at the lower of cost or market. The first-in, first-out method is the predominant method of inventory costing in Europe and Canada. The last-in, first-out (LIFO) method is the predominant method of inventory costing in the United States. At September 30, 2013 and December 31, 2012, the LIFO method accounted for 61 percent and 56 percent of total inventory values, respectively.
	(In millions)	September 30, 2013		December 31, 2012
	Raw materials	$	968	$	945
	Semi-finished products	877		883
	Finished products	535		573
	Supplies and sundry items	100		102
	Total	$	2,480	$	2,503
	Current acquisition costs were estimated to exceed the above inventory values by $1.1 billion and $1.0 billion at September 30, 2013 and December 31, 2012, respectively. Cost of sales was increased by $3 million and reduced by $5 million in the three months ended September 30, 2013 and 2012, respectively, as a result of the liquidation of LIFO inventories. Cost of sales was increased by $3 million and reduced by $16 million in the nine months ended September 30, 2013 and 2012, respectively, as a result of liquidation of LIFO inventories.
	Inventory includes $84 million and $86 million of property held for residential or commercial development as of September 30, 2013 and December 31, 2012, respectively.

Derivative_Instruments

Derivative Instruments	9 Months Ended
	Sep. 30, 2013
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments	Derivative Instruments
	U. S. Steel is exposed to foreign currency exchange rate risks as a result of our European and Canadian operations. USSE’s revenues are primarily in euros and costs are primarily in U.S. dollars and euros. USSC’s revenues and costs are denominated in both Canadian and U.S. dollars. In addition, foreign cash requirements have been, and in the future may be, funded by intercompany loans, creating intercompany monetary assets and liabilities in currencies other than the functional currency of the entities involved, which can affect income when remeasured at the end of each period.
	U. S. Steel uses euro forward sales contracts with maturities no longer than 12 months to exchange euros for U.S. dollars to manage our currency requirements and exposure to foreign currency exchange rate fluctuations. Derivative instruments are required to be recognized at fair value in the balance sheet. U. S. Steel has not elected to designate these euro forward sales contracts as hedges. Therefore, changes in their fair value are recognized immediately in the results of operations. The gains and losses recognized on these euro forward sales contracts may also partially offset the accounting remeasurement gains and losses recognized on intercompany loans.
	As of September 30, 2013, U. S. Steel held euro forward sales contracts with a total notional value of approximately $333 million. We mitigate the risk of concentration of counterparty credit risk by purchasing our forward sales contracts from several counterparties.
	Additionally, we routinely enter into fixed-price forward physical purchase contracts to partially manage our exposure to price risk related to the purchases of natural gas, electricity and certain nonferrous metals used in the production process. During 2013 and 2012, the forward physical purchase contracts for natural gas and nonferrous metals qualified for the normal purchases and normal sales exemption described in ASC Topic 815 and were not subject to mark-to-market accounting.
	The following summarizes the location and amounts of the fair values and gains or losses related to derivatives included in U. S. Steel’s financial statements as of September 30, 2013 and December 31, 2012 and for the three and nine months ended September 30, 2013 and 2012:
			Fair Value			Fair Value
	(In millions)	Balance Sheet	30-Sep-13			31-Dec-12
		Location
	Foreign exchange forward contracts	Accounts payable	$	9		$	12
		Statement of	Amount of Gain			Amount of Gain
		Operations	(Loss)			(Loss)
	(In millions)	Location	Three Months Ended September 30, 2013			Nine Months Ended September 30, 2013
	Foreign exchange forward contracts	Other financial	$	(11	)	$	(7	)
		costs
		Statement of	Amount of Gain			Amount of Gain
		Operations	(Loss)			(Loss)
	(In millions)	Location	Three Months Ended September 30, 2012			Nine Months Ended September 30, 2012
	Foreign exchange forward contracts	Other financial	$	(12	)	$	1
		costs
	In accordance with the guidance found in ASC Topic 820 on fair value measurements and disclosures, the fair value of our euro forward sales contracts was determined using Level 2 inputs, which are defined as “significant other observable” inputs. The inputs used are from market sources that aggregate data based upon market transactions.

Debt

Debt	9 Months Ended
	Sep. 30, 2013
Debt Disclosure [Abstract]
Debt	Debt
	(In millions)		Interest		Maturity	September 30, 2013		December 31, 2012
			Rates %
	2037 Senior Notes		6.65		2037	$	350	$	350
	2022 Senior Notes		7.5		2022	400		400
	2021 Senior Notes		6.875		2021	275		—
	2020 Senior Notes		7.375		2020	600		600
	2018 Senior Notes		7		2018	500		500
	2017 Senior Notes		6.05		2017	450		450
	2019 Senior Convertible Notes		2.75		2019	316		—
	2014 Senior Convertible Notes		4		2014	322		863
	Province Note (C$150 million)		1		2015	146		151
	Environmental Revenue Bonds		5.38 - 6.88		2015 - 2042	549		549
	Recovery Zone Facility Bonds		6.75		2040	70		70
	Fairfield Caster Lease				2022	35		35
	Other capital leases and all other obligations				2013 - 2014	—		1
	Amended Credit Agreement		Variable		2016	—		—
	USSK Revolver		Variable		2016	—		—
	USSK credit facility		Variable		2015	—		—
	Total Debt					4,013		3,969
	Less Province Note fair value adjustment					17		23
	Less unamortized discount					56		8
	Less short-term debt and long-term debt due within one year					322		2
	Long-term debt					$	3,618	$	3,936
	To the extent not otherwise discussed below, information concerning the Senior Notes, the 2014 Senior Convertible Notes and other listed obligations can be found in Note 14 of the audited financial statements in the 2012 Annual Report on Form 10-K.
	2021 Senior Notes
	On March 26, 2013, U. S. Steel issued $275 million of 6.875% Senior Notes due April 1, 2021 (2021 Senior Notes). U. S. Steel received net proceeds from the offering of $270 million after fees of $5 million related to the underwriting discount and third party expenses. The net proceeds from the issuance of the 2021 Senior Notes, together with the net proceeds of the concurrent 2019 Senior Convertible Notes offering (see below), were used to repurchase a portion of our 4.00% Senior Convertible Notes due May 15, 2014 (the 2014 Senior Convertible Notes). Interest on the 2021 Senior Notes is payable semi-annually on April 1st and October 1st of each year, commencing on October 1, 2013.
	U. S. Steel may redeem the 2021 Senior Notes, in whole or in part, at our option at any time and from time to time on or after April 1, 2017 at the redemption price for such notes set forth below as a percentage of the principal amount, plus accrued and unpaid interest to, but excluding, the redemption date, if redeemed during the twelve-month period beginning April 1 of the years indicated below:
	Year	Redemption Price
	2017	103.438	%
	2018	101.719	%
	2019 and thereafter	100	%
	2019 Senior Convertible Notes
	On March 26, 2013, U. S. Steel issued $316 million of 2.75% Senior Convertible Notes due April 1, 2019 (the 2019 Senior Convertible Notes). U. S. Steel received net proceeds from the offering of $306 million after fees of $10 million related to the underwriting discount and third party expenses. The net proceeds from the issuance of the 2019 Senior Convertible Notes, together with the net proceeds of the concurrent 2021 Senior Notes offering (see above), were used to repurchase a portion of our 2014 Senior Convertible Notes. Interest on the 2019 Senior Convertible Notes is payable semi-annually on April 1st and October 1st of each year, commencing on October 1, 2013.
	The initial conversion rate for the 2019 Senior Convertible Notes is 39.5491 shares of U. S. Steel common stock per $1,000 principal amount, equivalent to an initial conversion price of approximately $25.29 per share of common stock, subject to adjustment as defined in the 2019 Senior Convertible Notes. On the issuance date of the 2019 Senior Convertible Notes, the market price of U. S. Steel’s common stock was below the stated conversion price of $25.29 so there was no beneficial conversion option to the holders. Based on the initial conversion rate, the 2019 Senior Convertible Notes are convertible into 12,507,403 shares of U. S. Steel common stock and we reserved for the possible issuance of 16,259,615 shares, which is the maximum amount that could be issued upon conversion. Holders may convert their notes at their option prior to the close of business on the business day immediately preceding October 1, 2018 only under certain circumstances (as described in the 2019 Senior Convertible Notes). On or after October 1, 2018, until the close of business on the second scheduled trading day immediately preceding the maturity date, holders may convert their 2019 Senior Convertible Notes at any time. Upon conversion, we will satisfy our conversion obligation by paying or delivering, as the case may be, cash, shares of our common stock or a combination of cash and shares of our common stock at our election. Any unconverted 2019 Senior Convertible Notes mature at par on April 1, 2019.
	U. S. Steel may not redeem the 2019 Senior Convertible Notes prior to April 5, 2017. On or after April 5, 2017, we may redeem for cash all or part of the 2019 Senior Convertible Notes, at our option, under certain circumstances. The redemption price will equal 100% of the principal amount of the 2019 Senior Convertible Notes to be redeemed, plus accrued and unpaid interest to, but excluding, the redemption date.
	If U. S. Steel undergoes a fundamental change, as defined in the 2019 Senior Convertible Notes, holders may require us to repurchase the 2019 Senior Convertible Notes in whole or in part for cash at a price equal to 100% of the principal amount of the 2019 Senior Convertible Notes to be purchased plus any accrued and unpaid interest (including additional interest, if any) up to, but excluding the repurchase date.
	Although the 2019 Senior Convertible Notes were issued at par, for accounting purposes the proceeds received from the issuance of the notes are allocated between debt and equity to reflect the fair value of the conversion option embedded in the notes and the fair value of similar debt without the conversion option. As a result, $53 million of the gross proceeds of the 2019 Senior Convertible Notes was recorded as an increase in additional paid-in capital with the offsetting amount recorded as a debt discount. The debt discount will be amortized over the term of the 2019 Senior Convertible Notes using an interest rate of 6.2% (the estimated effective borrowing rate for nonconvertible debt at the time of issuance) which will accrete the carrying value of the notes to the principal amount at maturity. As of September 30, 2013, the remaining unamortized debt discount was $49 million and the net carrying amount of the 2019 Senior Convertible Notes was $267 million.
	Similar to our other senior notes, the 2019 Senior Convertible Notes and the 2021 Senior Notes contain covenants limiting our ability to create liens, to enter into sale-leaseback transactions and to consolidate, merge or transfer all, or substantially all of our assets. They also contain provisions requiring the purchase of the notes upon a change in control under certain specified circumstances, as well as other customary provisions. In addition, certain payment defaults on other indebtedness are a default under the 2019 Senior Convertible Notes.
	2014 Senior Convertible Notes
	In March 2013, U. S. Steel repurchased approximately $542 million aggregate principal amount of our 4.00% Senior Convertible Notes due 2014, reducing the outstanding principal amount of the notes to $322 million.
	The repurchases were funded with the net proceeds from the 2021 Senior Notes and the 2019 Senior Convertible Notes and cash. The aggregate purchase price, including accrued and unpaid interest and fees, for the convertible notes repurchased was approximately $580 million. U. S. Steel recorded a pretax charge of $34 million to net interest and other financial costs (see Note 7) in the first nine months of 2013 related mainly to the repurchase premiums.
	Amended Credit Agreement
	As of September 30, 2013, there were no amounts drawn on the Amended Credit Agreement, which expires July 20, 2016, and inventory values calculated in accordance with the Amended Credit Agreement supported the full $875 million of the facility. Under the Amended Credit Agreement, U. S. Steel must maintain a fixed charge coverage ratio (as further defined in the Amended Credit Agreement) of at least 1.00 to 1.00 for the most recent four consecutive quarters when availability under the Amended Credit Agreement is less than the greater of 10% of the total aggregate commitments and $87.5 million. Since availability was greater than $87.5 million, compliance with the fixed charge coverage ratio covenant was not applicable. Based on the most recent four quarters as of September 30, 2013, we would not meet this covenant. If the value of inventory does not support the full amount of the facility or we remain unable to meet this covenant in the future, the full amount of this facility would not be available to the Company.
	Receivables Purchase Agreement
	As of September 30, 2013, U. S. Steel has a Receivables Purchase Agreement (RPA) under which eligible trade accounts receivable are sold, on a daily basis without recourse, to U. S. Steel Receivables, LLC (USSR), a wholly owned, bankruptcy-remote, special purpose entity used only for the securitization program. As U. S. Steel accesses this facility, USSR sells senior undivided interests in the receivables to certain third-party commercial paper conduits, while maintaining a subordinated undivided interest in a portion of the receivables. U. S. Steel has agreed to continue servicing the sold receivables at market rates.
	At both September 30, 2013 and December 31, 2012, eligible accounts receivable supported $625 million of availability under the RPA and there were no receivables sold to third-party conduits under this facility.
	USSR pays the conduits a discount based on the conduits’ borrowing costs plus incremental fees. We paid $1 million in each of the three month periods ended September 30, 2013 and 2012 and $3 million in each of the nine month periods ended September 30, 2013 and 2012 relating to fees on the RPA. These costs are included in other financial costs in the Consolidated Statement of Operations.
	Generally, the facility provides that as payments are collected from the sold accounts receivables, USSR may elect to have the conduits reinvest the proceeds in new eligible accounts receivable. As there was no activity under this facility during the nine months ended September 30, 2013, there were no collections reinvested. During the nine months ended September 30, 2012, collection of accounts receivable of approximately $1,175 million were reinvested.
	The eligible accounts receivable and receivables sold to third-party conduits are summarized below:
	(In millions)		September 30, 2013			December 31, 2012
	Balance of accounts receivable-net, eligible for sale to third-party conduits		$	1,053		$	1,127
	Accounts receivable sold to third-party conduits		—			—
	Balance included in Receivables on the balance sheet of U. S. Steel		$	1,053		$	1,127
	The net book value of U. S. Steel’s retained interest in the receivables represents the best estimate of the fair market value due to the short-term nature of the receivables. The retained interest in the receivables is recorded net of the allowance for bad debts, which historically have not been significant.
	The facility may be terminated on the occurrence and failure to cure certain events, including, among others, failure of USSR to maintain certain ratios related to the collectability of the receivables and failure to make payment under its material debt obligations. The facility may also be terminated upon a change of control. The facility expires in July 2016.
	Change in control event
	If there is a change in control of U. S. Steel, the following may occur: (a) debt obligations totaling $3,212 million as of September 30, 2013 (including the Senior Notes and Senior Convertible Notes) may be declared immediately due and payable; (b) the Amended Credit Agreement, the RPA and USSK’s €200 million revolving credit agreement may be terminated and any amounts outstanding declared immediately due and payable; and (c) U. S. Steel may be required to either repurchase the leased Fairfield Works slab caster for $41 million or provide a letter of credit to secure the remaining obligation.
	U. S. Steel Košice (USSK) credit facilities
	At September 30, 2013, USSK had no borrowings under its €200 million (approximately $270 million) unsecured revolving credit facility.
	On July 15, 2013, USSK entered into a €200 million revolving credit facility agreement (the Credit Agreement) that replaced USSK's €200 million credit facility that was scheduled to expire in August 2013. The Credit Agreement contains certain USSK financial covenants (as further defined in the Credit Agreement) as well as other customary terms and conditions. The Credit Agreement expires in July 2016.
	At September 30, 2013, USSK had no borrowings under its €20 million unsecured credit facility (approximately $27 million) and the availability was approximately $25 million due to approximately $2 million of customs and other guarantees outstanding.

Asset_Retirement_Obligations

Asset Retirement Obligations	9 Months Ended
	Sep. 30, 2013
Asset Retirement Obligation Disclosure [Abstract]
Asset Retirement Obligations	Asset Retirement Obligations
	U. S. Steel’s asset retirement obligations (AROs) primarily relate to mine and landfill closure and post-closure costs. The following table reflects changes in the carrying values of AROs:
	(In millions)	September 30, 2013			December 31, 2012
	Balance at beginning of year	$	33		$	38
	Additional obligations incurred	5			2
	Obligations settled	(7		)	(9		)	(a)
	Accretion expense	4			2
	Balance at end of period	$	35		$	33
	(a) Includes $2 million as a result of the sale of USSS on January 31, 2012. See Note 4 for additional details.
	Certain AROs related to disposal costs of the majority of fixed assets at our integrated steel facilities have not been recorded because they have an indeterminate settlement date. These AROs will be initially recognized in the period in which sufficient information exists to estimate their fair value.

Fair_Value_of_Financial_Instru

Fair Value of Financial Instruments	9 Months Ended
	Sep. 30, 2013
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	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 Consolidated Balance Sheet approximate fair value. See Note 5 for disclosure of U. S. Steel's contingent consideration arrangement and Note 13 for disclosure of U. S. Steel’s derivative instruments, which are both accounted for at fair value on a recurring basis.
	The following table summarizes U. S. Steel’s financial assets and liabilities that were not carried at fair value at September 30, 2013 and December 31, 2012.
		30-Sep-13				December 31, 2012
	(In millions)	Fair		Carrying		Fair		Carrying
		Value		Amount		Value		Amount
	Financial assets:
	Investments and long-term receivables (a)	$	66	$	66	$	39	$	39
	Financial liabilities:
	Debt (b)	$	4,010	$	3,904	$	4,113	$	3,902
	(a) Excludes equity method investments.
	(b) Excludes capital lease obligations.
	The following methods and assumptions were used to estimate the fair value of financial instruments included in the table above:
	Investments and long-term receivables: Fair value was based on Level 2 inputs which were discounted cash flows. U. S. Steel is subject to market risk and liquidity risk related to its investments.
	Long-term debt instruments: Fair value was determined using Level 2 inputs which were derived from quoted market prices and is based on the yield on public debt where available or current borrowing rates available for financings with similar terms and maturities.
	Fair value of the financial assets and liabilities disclosed herein is not necessarily representative of the amount that could be realized or settled, nor does the fair value amount consider the tax consequences of realization or settlement.
	Financial guarantees are U. S. Steel’s only unrecognized financial instrument. For details relating to financial guarantees see Note 20.

Statement_of_Changes_in_Stockh

Statement of Changes in Stockholders' Equity	9 Months Ended
	Sep. 30, 2013
Equity [Abstract]
Statement of Changes in Stockholders' Equity	Statement of Changes in Stockholders’ Equity
	The following table reflects the first nine months of 2013 and 2012 reconciliation of the carrying amount of total equity, equity attributable to United States Steel Corporation and equity attributable to the noncontrolling interests:
	Nine Months Ended September 30, 2013 (In millions)	Total			Comprehensive			Retained			Accumulated			Common		Treasury			Paid-in			Non-
					Income (Loss)			Earnings			Other			Stock		Stock			Capital			Controlling
											Comprehensive											Interest
											Income (Loss)
	Balance at beginning of year	$	3,478					$	3,463		$	(3,268	)	$	151	$	(521	)	$	3,652		$	1
	Comprehensive income:
	Net loss	(1,942		)	(1,942		)	(1,942		)
	Other comprehensive income (loss), net of tax:
	Pension and other benefit adjustments	197			197						197
	Currency translation adjustment	13			13						13
	Issuance of conversion option in 2019 Senior Convertible Notes, net of tax	31																	31
	Employee stock plans	22														40			(18		)
	Dividends paid on common stock	(22		)				(22		)
	Other	(2		)				$	(2	)
	Balance at September 30, 2013	$	1,775		$	(1,732	)	$	1,497		$	(3,058	)	$	151	$	(481	)	$	3,665		$	1
	Nine Months Ended September 30, 2012 (In millions)	Total			Comprehensive			Retained			Accumulated			Common		Treasury			Paid-in			Non-
					Income (Loss)			Earnings			Other			Stock		Stock			Capital			Controlling
											Comprehensive											Interest
											Income (Loss)
	Balance at beginning of year	$	3,501					$	3,616		$	(3,367	)	$	151	$	(550	)	$	3,650		$	1
	Comprehensive income:
	Net loss	(74		)	(74		)	(74		)
	Other comprehensive income (loss), net of tax:
	Pension and other benefit adjustments	360			360						360
	Currency translation adjustment	76			76						76
	Employee stock plans	21														29			(8		)
	Dividends paid on common stock	(22		)				(22		)
	Other	1																				1
	Balance at September 30, 2012	$	3,863		$	362		$	3,520		$	(2,931	)	$	151	$	(521	)	$	3,642		$	2

Reclassifications_from_Accumul

Reclassifications from Accumulated Other Comprehensive Income (AOCI)	9 Months Ended
	Sep. 30, 2013
Equity [Abstract]
Reclassifications from Accumulated Other Comprehensive Income (AOCI)	Reclassifications from Accumulated Other Comprehensive Income (AOCI)
	(In millions) (a)		Pension and				Foreign				Total
			Other Benefit				Currency
			Items				Items
	Balance at December 31, 2012		$	(3,613	)		$	345			$	(3,268	)
	Other comprehensive income (loss) before reclassifications		(13		)		13				—
	Amounts reclassified from AOCI (b)		210				—				210
	Net current-period other comprehensive income		197				13				210
	Balance at September 30, 2013		$	(3,416	)		$	358			$	(3,058	)
	(a)All amounts are net of tax. Amounts in parentheses indicate debits.
	(b)See table below for further details.
					Amount reclassified
					from AOCI
	(In millions) (a)		Details about AOCI components		Three Months Ended September 30, 2013				Nine Months Ended September 30, 2013
			Amortization of pension and other benefit items
			Prior service costs		$	(3	)	(b)	$	(8	)	(b)
			Actuarial gains/(losses)		(100		)	(b)	(298		)	(b)
			Total before tax		(103		)		(306		)
			Tax benefit		29				96
			Net of tax		$	(74	)		$	(210	)
	(a)Amounts in parentheses indicate debits to income/loss.
	(b)	These AOCI components are included in the computation of net periodic benefit cost (see Note 6 for additional details).

Related_Party_Transactions

Related Party Transactions	9 Months Ended
	Sep. 30, 2013
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions
	Net sales to related parties and receivables from related parties primarily reflect sales of steel products to equity investees. Generally, transactions are conducted under long-term market-based contractual arrangements. Related party sales and service transactions were $275 million and $342 million for the three months ended September 30, 2013 and 2012, respectively, and $863 million and $1 billion for the nine months ended September 30, 2013 and 2012, respectively.
	Purchases from related parties for outside processing services provided by equity investees amounted to $18 million and $16 million for the three months ended September 30, 2013 and 2012, respectively, and $53 million and $44 million for the nine months ended September 30, 2013 and 2012, respectively. Purchases of iron ore pellets from related parties amounted to $63 million and $84 million for the three months ended September 30, 2013 and 2012, respectively and $180 million and $204 million for the nine months ended September 30, 2013 and 2012, respectively.
	Accounts payable to related parties include amounts collected on behalf of PRO-TEC Coating Company (PRO-TEC) of $89 million and $75 million at September 30, 2013 and December 31, 2012, respectively. U. S. Steel, as PRO-TEC’s exclusive sales agent, is responsible for credit risk related to PRO-TEC’s receivables. U. S. Steel also provides PRO-TEC marketing, selling and customer service functions. Payables to other related parties totaled $4 million and $3 million at September 30, 2013 and December 31, 2012, respectively.

Contingencies_and_Commitments

Contingencies and Commitments	9 Months Ended
	Sep. 30, 2013
Commitments and Contingencies Disclosure [Abstract]
Contingencies and Commitments	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 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.
	Asbestos matters – As of September 30, 2013, U. S. Steel was a defendant in approximately 800 active cases involving approximately 3,340 plaintiffs. Many of these cases involve multiple defendants (typically from fifty to more than one hundred). About 2,560, or approximately 77 percent, of these plaintiff claims are currently pending in jurisdictions which permit filings with massive numbers of 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. During the nine months ended September 30, 2013, U. S. Steel paid approximately $6 million in settlements. These settlements and other dispositions resolved approximately 175 claims. New case filings in the first nine months of 2013 added approximately 185 claims. At December 31, 2012, U. S. Steel was a defendant in approximately 790 active cases involving approximately 3,330 plaintiffs. During 2012, U. S. Steel paid approximately $15 million in settlements. These settlements and other dispositions resolved approximately 190 claims. New case filings in the year ended December 31, 2012 added approximately 285 claims. Most claims filed in 2013 and 2012 involved individual or small groups of claimants as many jurisdictions no longer permit the filing of mass complaints.
	Historically, these claims against U. S. Steel fall into three major groups: (1) claims made by persons who allegedly were exposed to asbestos at U. S. Steel facilities (referred to as “premises claims”); (2) claims made by industrial workers allegedly exposed to products manufactured by U. S. Steel; and (3) claims made under certain federal and general maritime laws by employees of former operations of U. S. Steel. In general, the only insurance available to U. S. Steel with respect to asbestos claims is excess casualty insurance, which has multi-million dollar retentions. To date, U. S. Steel has received minimal payments under these policies for asbestos claims.
	These asbestos cases allege a variety of respiratory and other diseases based on alleged exposure to asbestos. U. S. Steel is currently a defendant in cases in which a total of approximately 260 plaintiffs allege that they are suffering from mesothelioma. The potential for damages against defendants may be greater in cases where the plaintiffs can prove mesothelioma.
	In many cases, the plaintiffs have been unable to establish any causal relationship to U. S. Steel or its products or premises; however, with the decline in mass plaintiff cases, the incidence of claimants actually alleging a claim against U. S. Steel is increasing. In addition, in many asbestos cases, the claimants have been unable to demonstrate that they have suffered any identifiable injury or compensable loss at all; that any injuries that they have incurred did in fact result from alleged exposure to asbestos; or that such alleged exposure was in any way related to U. S. Steel or its products or premises.
	The amount U. S. Steel has accrued for pending asbestos claims is not material to U. S. Steel’s financial position. U. S. Steel does not accrue for unasserted asbestos claims because it is not possible to determine whether any loss is probable with respect to such claims or even to estimate the amount or range of any possible losses. The vast majority of pending claims against U. S. Steel allege so-called “premises” liability-based alleged exposure on U. S. Steel’s current or former premises. These claims are made by an indeterminable number of people such as truck drivers, railroad workers, salespersons, contractors and their employees, government inspectors, customers, visitors and even trespassers. In most cases the claimant also was exposed to asbestos in non-U. S. Steel settings; the relative periods of exposure between U. S. Steel and non-U. S. Steel settings vary with each claimant; and the strength or weakness of the causal link between U. S. Steel exposure and any injury vary widely as do the nature and severity of the injury claimed.
	We are unable to estimate the ultimate outcome of asbestos-related lawsuits, claims and proceedings due to the unpredictable nature of personal injury litigation. Despite this uncertainty, management believes that the ultimate resolution of these matters will not have a material adverse effect on U. S. Steel’s financial condition, although the resolution of such matters could significantly impact results of operations for a particular quarter. Among the factors considered in reaching this conclusion are: (1) it has been many years since U. S. Steel employed maritime workers or manufactured or sold asbestos containing products; (2) most asbestos containing material was removed or remediated at U. S. Steel facilities many years ago; and (3) U. S. Steel’s history of trial outcomes, settlements and dismissals.
	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 are summarized in the following table:
	(In millions)	Nine Months Ended September 30, 2013
	Beginning of period	$	203
	Accruals for environmental remediation deemed probable and reasonably estimable	5
	Payments	(9		)
	End of period	$	199
	Accrued liabilities for remediation activities are included in the following balance sheet lines:
	(In millions)		September 30, 2013			December 31, 2012
	Accounts payable		$	17		$	21
	Deferred credits and other noncurrent liabilities		182			182
	Total		$	199		$	203
	Expenses related to remediation are recorded in cost of sales and totaled less than $1 million and $2 million for the three months ended September 30, 2013 and 2012, respectively and $5 million and $11 million for the nine months ended September 30, 2013 and 2012, respectively. It is not presently possible to estimate the ultimate amount of all remediation costs that might be incurred. Due to uncertainties inherent in remediation projects and the associated liabilities, it is possible that total remediation costs for active matters and projects with ongoing study and scope development may exceed the accrued liabilities by as much as 20 to 40 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, we categorize projects as follows:
	-1	Projects with Ongoing Study and Scope Development are those projects which are still in the study and 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 cost estimates cannot be determined. Therefore, it is reasonably possible that material costs in addition to the accrued liabilities for these projects, may be incurred.
	-2	Significant Projects with Defined Scope are those projects with significant accrued liabilities, a defined scope and little likelihood of material additional costs.
	-3	Other Projects are those projects with relatively small accrued liabilities for which we believe that, while additional costs are possible, they are not likely to be material, and those projects for which we do not yet possess sufficient information to estimate potential costs to U. S. Steel.
	Projects with Ongoing Study and Scope Development – There are six environmental remediation projects where reasonably possible additional costs for completion are not currently estimable, but could be material. There are four Resource Conservation and Recovery Act (RCRA) program projects (at Fairfield Works, Lorain Tubular, USS-POSCO Industries (UPI) and the Fairless Plant), the St. Louis Estuary and Upland project in Duluth, Minnesota and a voluntary remediation program project at the former steel making plant at Joliet, Illinois. As of September 30, 2013, accrued liabilities for these projects totaled $23 million for the costs of ongoing studies, investigations, and design. The St. Louis Estuary and Upland project was previously considered a "significant project with defined scope"; however, further studies are being conducted which are likely to result in an expanded scope. 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 $45 million to $75 million. Depending on agency negotiations and other factors, the UPI and the St. Louis Estuary and Upland projects may become defined in 2013.
	Significant Projects with Defined Scope – As of September 30, 2013, a total of $57 million was accrued for projects at or related to Gary Works where the scope of work is defined.
	An additional project with defined scope greater than or equal to $5 million consists of a project at U. S. Steel’s former Geneva Works in Geneva, Utah. As of September 30, 2013, the accrued liability for this project totaled $64 million. U. S. Steel does not expect material additional costs related to this project.
	Other Projects – There are six 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, 2013 was $13 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 had an accrued liability of less than $1 million. The total accrued liability for these projects at September 30, 2013 was $8 million. We do 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 $28 million at September 30, 2013 and were based on known scopes of work.
	Administrative and Legal Costs – As of September 30, 2013, U. S. Steel had an accrued liability of $6 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 have not changed significantly from year to year.
	Capital Expenditures – For a number of years, U. S. Steel has made substantial capital expenditures to bring existing facilities into compliance with various laws relating to the environment. In the first nine months of 2013 and 2012, such capital expenditures totaled $36 million and $37 million, respectively. U. S. Steel anticipates making additional such expenditures in the future; however, the exact amounts and timing of such expenditures are uncertain because of the continuing evolution of specific regulatory requirements.
	CO2 Emissions – Current and potential regulation of Greenhouse Gas (GHG) emissions remains a significant issue for the steel industry, particularly for integrated steel producers such as U. S. Steel. The regulation of carbon dioxide (CO2) emissions has either become law or is being considered by legislative bodies of many nations, including countries where we have operating facilities. The European Union (EU) has established GHG regulations based upon national allocations and a cap and trade system. In Canada, both the federal and Ontario governments have issued proposed requirements for GHG emissions. In the United States, the Environmental Protection Agency (EPA) has published rules for regulating GHG emissions for certain facilities and has implemented various reporting requirements as further described below. In 2010, GHG legislation was passed in the House of Representatives and introduced in the Senate. The federal courts are considering several suits that challenge the EPA’s authority to regulate GHG emissions under the Clean Air Act. We do not know what action, if any, may be taken by the current or future sessions of Congress.
	The EU has imposed limitations under the Emission Trading System for the period 2013-2020 (NAP III) that are more stringent than those in NAP II, reducing the number of free allowances granted to companies to cover their CO2 emissions. In September of 2013, the EC issued EU wide legislation further reducing the expected free allocation for NAP III by an average of approximately 12% for the NAP III period. The final volume of the free allocation for NAP III is expected to be published by the end of 2013.
	On May 13, 2010, the EPA published its final Greenhouse Gas Tailoring Rule establishing a mechanism for regulating GHG emissions from facilities through the Clean Air Act’s Prevention of Significant Deterioration (PSD) permitting process. U. S. Steel reported its emissions under these rules in accordance with the regulation and its deadlines. Since 2011, new projects that increase GHG emissions by more than 75,000 tons per year have new PSD requirements based on best available control technology (BACT), but only if the project also significantly increases emissions of at least one non-GHG pollutant. Only existing sources with Title V permits or new sources obtaining Title V permits for non-GHG pollutants will also be required to address GHG emissions. As of July 1, 2011, new sources not already subject to Title V requirements that emit over 100,000 tons per year, or modifications to existing permits that increase GHG emissions by more than 75,000 tons per year, are subject to PSD and Title V requirements. On November 17, 2010 the EPA issued its “PSD and Title V Permitting Guidance for Greenhouse Gases” and “Available and Emerging Technologies for Reducing Greenhouse Gas Emissions from the Iron and Steel Industry.” With this guidance, EPA intends to help state and local air permitting authorities identify greenhouse gas reductions under the Clean Air Act. Additionally, the EPA revised the National Ambient Air Quality Standards (NAAQS) for nitrogen oxide, sulfur dioxide and lead in 2010 and is in the process of revising the NAAQS for 2.5 micron particulate matter, ozone and sulfur dioxides.
	It is impossible to estimate the timing or impact of these or other future government action on U. S. Steel, although it could be significant. Such impacts may include substantial capital expenditures, costs for emission allowances, restriction of production, and higher prices for coking coal, natural gas and electricity generated by carbon based systems.
	European Union (EU) Environmental Requirements – Slovakia is currently considering a law implementing an EU Waste Framework Directive that would more strictly regulate waste disposal and increase fees for waste disposed of in landfills including privately owned landfills. The intent of the waste directive is to encourage recycling. Because Slovakia has not adopted implementing legislation, we cannot estimate the full financial impact of this prospective legislation at this time.
	The EU’s Industry Emission Directive will require implementation of EU determined best available techniques (BATs) to reduce environmental impacts as well as compliance with BAT associated emission levels. It contains operational requirements for air emissions, waste water discharges, solid waste disposal and energy conservation, dictates certain operating practices and imposes stricter emission limits. Producers will be required to be in compliance with the iron and steel BAT by March 8, 2016. We are evaluating the costs of complying with BAT, but our most recent broad estimate of likely capital expenditures is $300 million to $400 million over the 2013 to 2016 period. We are currently investigating the possibility of obtaining EU grants to fund a portion of those capital expenditures. We also believe that there will be increased operating costs, such as increased energy and maintenance costs, but we are currently unable to reliably estimate them.
	Environmental and other 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 sold. These indemnifications and cost sharing agreements have related to the condition of the property, the approved use, certain representations and warranties, matters of title and environmental matters. While most of these provisions have not specifically dealt with environmental issues, there have been transactions in which U. S. Steel indemnified the buyer for non-compliance with past, current and future environmental laws related to existing conditions and there can be questions as to the applicability of more general indemnification provisions to environmental matters. Most recent indemnifications and cost sharing agreements are of a limited nature only applying to non-compliance with past and/or current laws. Some indemnifications and cost sharing agreements only run for a specified period of time after the transactions close and others run indefinitely. In addition, current owners of property formerly owned by U. S. Steel may have common law claims and contribution rights against U. S. Steel for environmental matters. 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 sold. Aside from the environmental liabilities already recorded as a result of these transactions due to specific environmental remediation activities and cases (included in the $199 million of accrued liabilities for remediation discussed above), there are no other known environmental liabilities related to these transactions.
	Guarantees – The maximum guarantees of the indebtedness of unconsolidated entities of U. S. Steel totaled $29 million (which includes the recorded liability of $22 million noted below) at September 30, 2013. If any default related to the guaranteed indebtedness occurs, U. S. Steel has access to its interest in the assets of the investees to reduce its potential losses under the guarantees.
	During the third quarter of 2013, U. S. Steel recorded a pretax charge of $22 million to net interest and other financial costs (see Note 7) to record a liability related to a guarantee of debt related to an unconsolidated equity investment for which payment by U. S. Steel is probable. The $22 million is the maximum amount U. S. Steel would be obligated to pay as the guarantor and represents the fair value of the obligation at September 30, 2013.
	Antitrust Class Actions – In a series of lawsuits filed in federal court in the Northern District of Illinois beginning September 12, 2008, individual direct or indirect buyers of steel products have asserted that eight steel manufacturers, including U. S. Steel, conspired in violation of antitrust laws to restrict the domestic production of raw steel and thereby to fix, raise, maintain or stabilize the price of steel products in the United States. The cases are filed as class actions and claim treble damages for the period 2005 to present, but do not allege any damage amounts. U. S. Steel is vigorously defending these lawsuits and does not believe that it is probable a liability regarding these matters has been incurred. We are unable to estimate a range of possible loss at this time.
	EPA Region V Federal Lawsuit – On August 1, 2012, the U.S. government, joined by the States of Illinois, Indiana and Michigan, filed a complaint in the Northern District of Indiana alleging various CAA and State air regulatory violations that were to have allegedly occurred at Gary Works, Granite City Works, and Great Lakes Works, our three integrated iron and steel facilities located in EPA Region V. The Complaint alleges that Gary Works failed to obtain the proper pre-construction permit for a routine reline of its Blast Furnace No. 4 in 1990, and that the three facilities failed to meet certain operational, maintenance, opacity, and recordkeeping requirements under the CAA and its implementing regulations. The Complaint requests relief in the form of statutory penalties for each violation and for injunctive relief. U. S. Steel believes that the claims asserted in the Complaint are not justified and are without statutory foundation. On September 21, 2012, U. S. Steel filed a motion to dismiss the U.S. government’s claims for relief regarding the 1990 reline of the Gary Blast Furnace No. 4 and filed an answer to the remaining allegations in the Complaint. On August 21, 2013, the district court issued an Opinion and Order, granting in part, and denying in part, the Motion to Dismiss. The court granted the Motion to Dismiss with respect to penalties such that the government is barred from seeking any civil penalties. However, the court denied our Motion to Dismiss with respect to injunctive relief. On September 6, 2013, U. S. Steel filed a Motion for Reconsideration to the district court with respect to its denial of the Motion to Dismiss regarding injunctive relief. In response, on September 26, 2013, the court issued a Notice of Hearing regarding U. S. Steel's Motion for Reconsideration for November 5, 2013. In the interim, the parties are continuing with discovery. U. S. Steel will continue to vigorously defend against these claims. At this time, the potential outcome is not reasonably estimable.
	Randle Reef – The Canadian and Ontario governments have identified for remediation a sediment deposit, commonly referred to as Randle Reef, in Hamilton Harbor near USSC’s Hamilton Works, for which the regulatory agencies estimate expenditures with a net present value of approximately C$120 million (approximately $117 million). The national and provincial governments have each allocated C$40 million (approximately $39 million) for this project. Local sources, including industry, have also agreed to provide funding of C$40 million (approximately $39 million) for this project. USSC has committed to contribute approximately 11,000 tons of hot rolled steel and to fund C$2 million (approximately $2 million). The steel contribution is expected to be made in 2014. As of September 30, 2013, U. S. Steel has an accrued current liability of approximately $10 million reflecting the contribution commitment.
	Other contingencies – Under certain operating 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 $16 million at September 30, 2013). 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 $168 million as of September 30, 2013, which reflects U. S. Steel’s maximum exposure under these financial guarantees, but not its total exposure for the underlying obligations. Most of the trust arrangements and letters of credit are collateralized by restricted cash. Restricted cash, which is recorded in other current and noncurrent assets, totaled $142 million at September 30, 2013, of which $1 million was classified as current, and $181 million at December 31, 2012, of which $5 million was classified as current. Restricted cash at September 30, 2013 also includes $50 million to fund certain capital projects at Gary Works, our Clairton Plant and Granite City Works. The proceeds become unrestricted as capital expenditures for these projects are made.
	Capital Commitments – At September 30, 2013, U. S. Steel’s contractual commitments to acquire property, plant and equipment totaled $235 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 2013		2014		2015	2016		2017	Later	Total
									Years
	$307		$806		$431	$332		$323	$1,728	$	3,927
	The majority of U. S. Steel’s unconditional purchase obligations relates to the supply of industrial gases, energy and utility services with terms ranging from two to 15 years. Unconditional purchase obligations also include coke and steam purchase commitments related to a coke supply agreement with Gateway Energy & Coke Company LLC under which Gateway is obligated to supply 90 percent to 105 percent of the expected annual capacity of the heat recovery coke plant at our Granite City Works, and U. S. Steel is obligated to purchase the coke from Gateway at the contract price. As of September 30, 2013, a maximum default payment of approximately $250 million would apply if U. S. Steel terminates the agreement.
	Total payments relating to unconditional purchase obligations were approximately $115 million and $180 million for the three months ended September 30, 2013 and 2012, respectively and $410 million and $550 million for the nine months ended September 30, 2013 and 2012, respectively.

Subsequent_Event

Subsequent Event	9 Months Ended
	Sep. 30, 2013
Subsequent Events [Abstract]
Subsequent Event	Subsequent Event
	In October of 2013, U. S. Steel decided to permanently shut down its iron and steelmaking facilities at Hamilton Works on December 31, 2013. As a result, we expect to record a non-cash charge in the fourth quarter of 2013 of approximately $225 million for accelerated depreciation on the associated fixed assets.

Basis_of_Presentation_Policies

Basis of Presentation (Policies)	9 Months Ended
	Sep. 30, 2013
Accounting Policies [Abstract]
Reclassifications	Reclassifications
	Certain reclassifications of prior years’ data have been made to conform to the current year presentation.

Segment_Information_Tables

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2013
Segment Reporting [Abstract]
Results of Segment Operations	The results of segment operations for the three months ended September 30, 2013 and 2012 are:
	(In millions) Third Quarter 2013	Customer			Intersegment			Net			Income			Income
		Sales			Sales			Sales			(loss)			(loss)
											from			from
											investees			operations
	Flat-rolled	$	2,731		$	324		$	3,055		$	28		$	82
	USSE	643			1			644			—			(32		)
	Tubular	731			2			733			(1		)	49
	Total reportable segments	4,105			327			4,432			27			99
	Other Businesses	26			32			58			(1		)	14
	Reconciling Items and Eliminations	—			(359		)	(359		)	—			(1,815		)
	Total	$	4,131		$	—		$	4,131		$	26		$	(1,702	)
	Third Quarter 2012
	Flat-rolled	$	3,142		$	415		$	3,557		$	49		$	29
	USSE	696			68			764			—			27
	Tubular	787			3			790			(1		)	102
	Total reportable segments	4,625			486			5,111			48			158
	Other Businesses	27			13			40			—			13
	Reconciling Items and Eliminations	—			(499		)	(499		)	—			(109		)
	Total	$	4,652		$	—		$	4,652		$	48		$	62
	The results of segment operations for the nine months ended September 30, 2013 and 2012 are:
	(In millions) First Nine Months 2013	Customer			Intersegment			Net			Income			Income
		Sales			Sales			Sales			(loss)			(loss)
											from			from
											investees			operations
	Flat-rolled	$	8,710		$	985		$	9,695		$	41		$	18
	USSE	2,204			3			2,207			—			16
	Tubular	2,126			4			2,130			(7		)	158
	Total reportable segments	13,040			992			14,032			34			192
	Other Businesses	115			101			216			(3		)	62
	Reconciling Items and Eliminations	—			(1,093		)	(1,093		)	—			(1,925		)
	Total	$	13,155		$	—		$	13,155		$	31		$	(1,671	)
	First Nine Months 2012
	Flat-rolled	$	9,798		$	1,297		$	11,095		$	122		$	389
	USSE	2,274			143			2,417			—			27
	Tubular	2,604			6			2,610			(4		)	334
	Total reportable segments	14,676			1,446			16,122			118			750
	Other Businesses	165			105			270			(2		)	46
	Reconciling Items and Eliminations	—			(1,551		)	(1,551		)	—			(554		)
	Total	$	14,841		$	—		$	14,841		$	116		$	242
Segment Information	The following is a schedule of reconciling items to income (loss) from operations:
		Three Months Ended September 30,						Nine Months Ended September 30,
	(In millions)	2013			2012			2013			2012
	Items not allocated to segments:
	Postretirement benefit expense(a)	$	(55	)	$	(74	)	$	(165	)	$	(228	)
	Other items not allocated to segments:
	Impairment of goodwill (Note 5)	$	(1,783	)	—			$	(1,783	)	—
	Supplier contract dispute settlement	23			$	—		23			$	—
	Labor agreement lump sum payments(b)	—			(35		)	—			(35		)
	Net loss on the sale of assets (Note 4)	—			—			—			(310		)
	Property tax settlements	—			—			—			19
	Total other items not allocated to segments	(1,760		)	(35		)	(1,760		)	(326		)
	Total reconciling items	$	(1,815	)	$	(109	)	$	(1,925	)	$	(554	)
	(a) Consists of the net periodic benefit cost elements, other than service cost and amortization of prior service cost for active employees, associated with our pension, retiree health care and life insurance benefit plans.
	(b) Effective September 1, 2012, U. S. Steel and its U. S. Steel Tubular Products, Inc. subsidiary reached new labor agreements (the 2012 Labor Agreements) with the United Steel Workers (USW). The 2012 Labor Agreements provided for a $2,000 lump sum payment for each covered active USW member, which resulted in U. S. Steel recognizing a pretax charge of $35 million in the third quarter of 2012.

Goodwill_and_Intangible_Assets1

Goodwill and Intangible Assets (Tables)	9 Months Ended
	Sep. 30, 2013
Goodwill and Intangible Assets Disclosure [Abstract]
Changes in Carrying Amount of Goodwill by Segment	The changes in the carrying amount of goodwill by segment for the nine months ended September 30, 2013 are as follows:
		Flat-rolled				USSE				Tubular				Total
		Segment				Segment				Segment
	Balance at December 31, 2012	$	984			$	4			$	834			$	1,822
	Goodwill from acquisitions	—				—				3				$	3
	Impairment	(946		)		—				(837		)		(1,783		)
	Currency translation	(38		)		—				—				(38		)
	Balance at September 30, 2013	$	—			$	4			$	—			$	4
Amortizable Intangible Assets	Amortizable intangible assets are being amortized on a straight-line basis over their estimated useful lives and are detailed below:
				As of September 30, 2013												As of December 31, 2012
	(In millions)	Useful		Gross				Accumulated				Net				Gross		Accumulated		Net
		Lives		Carrying				Amortization				Amount				Carrying		Amortization		Amount
				Amount												Amount
	Customer relationships	22-23 Years		$	218			$	61			$	157			$	221	$	54	$	167
	Other	2-20 Years		23				12				11				22		11		11
	Total amortizable intangible assets			$	241			$	73			$	168			$	243	$	65	$	178

Pensions_and_Other_Benefits_Ta

Pensions and Other Benefits (Tables)	9 Months Ended
	Sep. 30, 2013
Compensation and Retirement Disclosure [Abstract]
Net Periodic Benefit Cost	The following table reflects the components of net periodic benefit cost for the three months ended September 30, 2013 and 2012:
		Pension						Other
		Benefits						Benefits
	(In millions)	2013			2012			2013			2012
	Service cost	$	32		$	29		$	7		$	7
	Interest cost	100			117			35			42
	Expected return on plan assets	(152		)	(154		)	(33		)	(29		)
	Amortization of prior service cost	6			6			(3		)	3
	Amortization of actuarial net loss	92			88			8			1
	Net periodic benefit cost, excluding below	78			86			14			24
	Multiemployer plans	19			18			—			—
	Settlement, termination and curtailment losses	$	3		$	—		$	—		$	—
	Net periodic benefit cost	$	100		$	104		$	14		$	24
	The following table reflects the components of net periodic benefit cost for the nine months ended September 30, 2013 and 2012:
		Pension						Other
		Benefits						Benefits
	(In millions)	2013			2012			2013			2012
	Service cost	$	96		$	88		$	21		$	22
	Interest cost	303			350			106			133
	Expected return on plan assets	(459		)	(460		)	(98		)	(86		)
	Amortization of prior service cost	18			15			(10		)	14
	Amortization of actuarial net loss	275			264			23			1
	Net periodic benefit cost, excluding below	233			257			42			84
	Multiemployer plans	55			52			—			—
	Settlement, termination and curtailment losses (gains)	3			(2		)	—			—
	Net periodic benefit cost	$	291		$	307		$	42		$	84

StockBased_Compensation_Plans_

Stock-Based Compensation Plans (Tables)	9 Months Ended
	Sep. 30, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Summary of Awards Made under Plans	The following table is a general summary of the awards made under the Plan.
		2013 Grants					2012 Grants
	Grant Details	Shares (a)		Fair Value (b)			Shares (a)		Fair Value (b)
	Executive Stock Options	826,340		$	8.37		510,570		$	11.93
	Non-executive Stock Options	970,640		$	9.7		993,310		$	11.93
	Restricted Stock Units	1,033,210		$	18.58		910,011		$	22.28
	Performance Awards (c)	271,960		$	21.26		328,780		$	25.26
	(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 year.
	(c) The number of Performance Awards shown represents the target value of the award.
Black-Scholes Assumptions	Compensation expense for stock options is recorded over the vesting period based on the fair value on the date of grant, as calculated by U. S. Steel using the Black-Scholes model and the assumptions listed below. The stock options vest ratably over a three-year service period and have a term of ten years.
	Black-Scholes Assumptions(a)		2013 Executive Grants			2013 Non-Executive Grants				2012 Grants
	Grant date price per share of option award		$	18.48		$	18.64			$	22.28
	Exercise price per share of option award		$	25		$	18.64			$	22.28
	Expected annual dividends per share, at grant date		$	0.2		$	0.2			$	0.2
	Expected life in years		5			5				5
	Expected volatility		66		%	67		%		68		%
	Risk-free interest rate		1.315		%	1.049		%		0.8		%
	Grant date fair value per share of unvested option awards as calculated from above		$	8.37		$	9.7			$	11.93

Significant_Equity_Investments1

Significant Equity Investments (Tables)	9 Months Ended
	Sep. 30, 2013
Equity Method Investments and Joint Ventures [Abstract]
Summarized Unaudited Income Statement Information for Significant Equity Investments	Summarized unaudited income statement information for our significant equity investments for the nine months ended September 30, 2013 and 2012 is reported below (amounts represent 100% of investee financial information):
	(In millions)	2013		2012
	Net sales	$	1,841	$	1,982
	Cost of sales	1,395		1,421
	Operating income	399		533
	Net income	382		521
	Net income attributable to significant equity investments	382		521

Earnings_and_Dividends_Per_Com1

Earnings and Dividends Per Common Share (Tables)	9 Months Ended
	Sep. 30, 2013
Earnings Per Share [Abstract]
Computations for Basic and Diluted Income (Loss) Per Common Share from Continuing Operations	The computations for basic and diluted earnings per common share from continuing operations are as follows:
		Three Months Ended September 30,							Nine Months Ended September 30,
	(Dollars in millions, except per share amounts)	2013				2012			2013			2012
	Net (loss) income attributable to United States Steel
	Corporation shareholders	$	(1,791	)		$	44		$	(1,942	)	$	(74	)
	Plus income effect of assumed conversion-interest on convertible notes	—				5			—			—
	Net (loss) income after assumed conversion	$	(1,791	)		$	49		$	(1,942	)	$	(74	)
	Weighted-average shares outstanding (in thousands):
	Basic	144,727				144,350			144,523			144,199
	Effect of convertible notes	—				27,059			—			—
	Effect of stock options, restricted stock units and performance awards	—				264			—			—
	Adjusted weighted-average shares outstanding, diluted	144,727				171,673			144,523			144,199
	Basic earnings per common share	$	(12.38	)		$	0.3		$	(13.44	)	$	(0.51	)
	Diluted earnings per common share	$	(12.38	)		$	0.28		$	(13.44	)	$	(0.51	)
Antidilutive Securities that were Not Included in Computations of Diluted Income (Loss) Per Common Share	The following table summarizes the securities that were antidilutive, and therefore, were not included in the computations of diluted earnings per common share:
		Three Months Ended September 30,						Nine Months Ended September 30,
	(In thousands)	2013			2012			2013		2012
	Securities granted under the 2005 Stock Incentive Plan	7,621			4,352			7,621		4,353
	Securities convertible under the Senior Convertible Notes	10,058			—			15,351	(a)	27,059
	Total	17,679			4,352			22,972		31,412
	(a) On March 27, 2013, we repurchased approximately $542 million aggregate principal amount of our 4% Senior Convertible Notes due in 2014. If the repurchases had occurred on January 1, 2013, the antidilutive securities would be 10,058 for the nine months ended September 30, 2013.

Inventories_Tables

Inventories (Tables)	9 Months Ended
	Sep. 30, 2013
Inventory Disclosure [Abstract]
Inventories
	(In millions)	September 30, 2013		December 31, 2012
	Raw materials	$	968	$	945
	Semi-finished products	877		883
	Finished products	535		573
	Supplies and sundry items	100		102
	Total	$	2,480	$	2,503

Derivative_Instruments_Tables

Derivative Instruments (Tables)	9 Months Ended
	Sep. 30, 2013
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Location and Amounts of Fair Values Related to Derivatives in Financial Statements
			Fair Value			Fair Value
	(In millions)	Balance Sheet	30-Sep-13			31-Dec-12
		Location
	Foreign exchange forward contracts	Accounts payable	$	9		$	12
Location and Amounts of Gains or Losses Related to Derivatives in Financial Statements
		Statement of	Amount of Gain			Amount of Gain
		Operations	(Loss)			(Loss)
	(In millions)	Location	Three Months Ended September 30, 2013			Nine Months Ended September 30, 2013
	Foreign exchange forward contracts	Other financial	$	(11	)	$	(7	)
		costs
		Statement of	Amount of Gain			Amount of Gain
		Operations	(Loss)			(Loss)
	(In millions)	Location	Three Months Ended September 30, 2012			Nine Months Ended September 30, 2012
	Foreign exchange forward contracts	Other financial	$	(12	)	$	1
		costs

Debt_Tables

Debt (Tables)	9 Months Ended
	Sep. 30, 2013
Debt Disclosure [Abstract]
Debt
	(In millions)		Interest		Maturity	September 30, 2013		December 31, 2012
			Rates %
	2037 Senior Notes		6.65		2037	$	350	$	350
	2022 Senior Notes		7.5		2022	400		400
	2021 Senior Notes		6.875		2021	275		—
	2020 Senior Notes		7.375		2020	600		600
	2018 Senior Notes		7		2018	500		500
	2017 Senior Notes		6.05		2017	450		450
	2019 Senior Convertible Notes		2.75		2019	316		—
	2014 Senior Convertible Notes		4		2014	322		863
	Province Note (C$150 million)		1		2015	146		151
	Environmental Revenue Bonds		5.38 - 6.88		2015 - 2042	549		549
	Recovery Zone Facility Bonds		6.75		2040	70		70
	Fairfield Caster Lease				2022	35		35
	Other capital leases and all other obligations				2013 - 2014	—		1
	Amended Credit Agreement		Variable		2016	—		—
	USSK Revolver		Variable		2016	—		—
	USSK credit facility		Variable		2015	—		—
	Total Debt					4,013		3,969
	Less Province Note fair value adjustment					17		23
	Less unamortized discount					56		8
	Less short-term debt and long-term debt due within one year					322		2
	Long-term debt					$	3,618	$	3,936
Redemption Price of 2021 Senior Notes as Percentage of Principal Amount Plus Accrued and Unpaid Interest to, but Excluding, Redemption Date	U. S. Steel may redeem the 2021 Senior Notes, in whole or in part, at our option at any time and from time to time on or after April 1, 2017 at the redemption price for such notes set forth below as a percentage of the principal amount, plus accrued and unpaid interest to, but excluding, the redemption date, if redeemed during the twelve-month period beginning April 1 of the years indicated below:
	Year	Redemption Price
	2017	103.438	%
	2018	101.719	%
	2019 and thereafter	100	%
Eligible Accounts Receivable and Receivables Sold to Third-Party Conduits	The eligible accounts receivable and receivables sold to third-party conduits are summarized below:
	(In millions)		September 30, 2013			December 31, 2012
	Balance of accounts receivable-net, eligible for sale to third-party conduits		$	1,053		$	1,127
	Accounts receivable sold to third-party conduits		—			—
	Balance included in Receivables on the balance sheet of U. S. Steel		$	1,053		$	1,127

Asset_Retirement_Obligations_T

Asset Retirement Obligations (Tables)	9 Months Ended
	Sep. 30, 2013
Asset Retirement Obligation Disclosure [Abstract]
Changes in Carrying Values of Asset Retirement Obligations	The following table reflects changes in the carrying values of AROs:
	(In millions)	September 30, 2013			December 31, 2012
	Balance at beginning of year	$	33		$	38
	Additional obligations incurred	5			2
	Obligations settled	(7		)	(9		)	(a)
	Accretion expense	4			2
	Balance at end of period	$	35		$	33
	(a) Includes $2 million as a result of the sale of USSS on January 31, 2012. See Note 4 for additional details.

Fair_Value_of_Financial_Instru1

Fair Value of Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2013
Fair Value Disclosures [Abstract]
Financial Assets and Liabilities Not Carried at Fair Value	The following table summarizes U. S. Steel’s financial assets and liabilities that were not carried at fair value at September 30, 2013 and December 31, 2012.
		30-Sep-13				December 31, 2012
	(In millions)	Fair		Carrying		Fair		Carrying
		Value		Amount		Value		Amount
	Financial assets:
	Investments and long-term receivables (a)	$	66	$	66	$	39	$	39
	Financial liabilities:
	Debt (b)	$	4,010	$	3,904	$	4,113	$	3,902
	(a) Excludes equity method investments.
	(b) Excludes capital lease obligations.

Statement_of_Changes_in_Stockh1

Statement of Changes in Stockholders' Equity (Tables)	9 Months Ended
	Sep. 30, 2013
Equity [Abstract]
Consolidated Statement of Changes in Equity	The following table reflects the first nine months of 2013 and 2012 reconciliation of the carrying amount of total equity, equity attributable to United States Steel Corporation and equity attributable to the noncontrolling interests:
	Nine Months Ended September 30, 2013 (In millions)	Total			Comprehensive			Retained			Accumulated			Common		Treasury			Paid-in			Non-
					Income (Loss)			Earnings			Other			Stock		Stock			Capital			Controlling
											Comprehensive											Interest
											Income (Loss)
	Balance at beginning of year	$	3,478					$	3,463		$	(3,268	)	$	151	$	(521	)	$	3,652		$	1
	Comprehensive income:
	Net loss	(1,942		)	(1,942		)	(1,942		)
	Other comprehensive income (loss), net of tax:
	Pension and other benefit adjustments	197			197						197
	Currency translation adjustment	13			13						13
	Issuance of conversion option in 2019 Senior Convertible Notes, net of tax	31																	31
	Employee stock plans	22														40			(18		)
	Dividends paid on common stock	(22		)				(22		)
	Other	(2		)				$	(2	)
	Balance at September 30, 2013	$	1,775		$	(1,732	)	$	1,497		$	(3,058	)	$	151	$	(481	)	$	3,665		$	1
	Nine Months Ended September 30, 2012 (In millions)	Total			Comprehensive			Retained			Accumulated			Common		Treasury			Paid-in			Non-
					Income (Loss)			Earnings			Other			Stock		Stock			Capital			Controlling
											Comprehensive											Interest
											Income (Loss)
	Balance at beginning of year	$	3,501					$	3,616		$	(3,367	)	$	151	$	(550	)	$	3,650		$	1
	Comprehensive income:
	Net loss	(74		)	(74		)	(74		)
	Other comprehensive income (loss), net of tax:
	Pension and other benefit adjustments	360			360						360
	Currency translation adjustment	76			76						76
	Employee stock plans	21														29			(8		)
	Dividends paid on common stock	(22		)				(22		)
	Other	1																				1
	Balance at September 30, 2012	$	3,863		$	362		$	3,520		$	(2,931	)	$	151	$	(521	)	$	3,642		$	2

Reclassifications_from_Accumul1

Reclassifications from Accumulated Other Comprehensive Income (AOCI) (Tables)	9 Months Ended
	Sep. 30, 2013
Equity [Abstract]
Other Comprehensive Income Activity Net of Tax
	(In millions) (a)		Pension and				Foreign				Total
			Other Benefit				Currency
			Items				Items
	Balance at December 31, 2012		$	(3,613	)		$	345			$	(3,268	)
	Other comprehensive income (loss) before reclassifications		(13		)		13				—
	Amounts reclassified from AOCI (b)		210				—				210
	Net current-period other comprehensive income		197				13				210
	Balance at September 30, 2013		$	(3,416	)		$	358			$	(3,058	)
	(a)All amounts are net of tax. Amounts in parentheses indicate debits.
	(b)See table below for further details.
Defined Benefit Plan In other Comprehensive Income
					Amount reclassified
					from AOCI
	(In millions) (a)		Details about AOCI components		Three Months Ended September 30, 2013				Nine Months Ended September 30, 2013
			Amortization of pension and other benefit items
			Prior service costs		$	(3	)	(b)	$	(8	)	(b)
			Actuarial gains/(losses)		(100		)	(b)	(298		)	(b)
			Total before tax		(103		)		(306		)
			Tax benefit		29				96
			Net of tax		$	(74	)		$	(210	)
	(a)Amounts in parentheses indicate debits to income/loss.
	(b)	These AOCI components are included in the computation of net periodic benefit cost (see Note 6 for additional details).

Contingencies_and_Commitments_

Contingencies and Commitments (Tables)	9 Months Ended
	Sep. 30, 2013
Commitments and Contingencies Disclosure [Abstract]
Changes in Accrued Liabilities for Remediation Activities	Changes in accrued liabilities for remediation activities are summarized in the following table:
	(In millions)	Nine Months Ended September 30, 2013
	Beginning of period	$	203
	Accruals for environmental remediation deemed probable and reasonably estimable	5
	Payments	(9		)
	End of period	$	199
Accrued Liabilities for Remediation Activities Included in Balance Sheet	Accrued liabilities for remediation activities are included in the following balance sheet lines:
	(In millions)		September 30, 2013			December 31, 2012
	Accounts payable		$	17		$	21
	Deferred credits and other noncurrent liabilities		182			182
	Total		$	199		$	203
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 2013		2014		2015	2016		2017	Later	Total
									Years
	$307		$806		$431	$332		$323	$1,728	$	3,927

Segment_Information_Results_of

Segment Information - Results of Segment Operations (Detail) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Segment Reporting Information [Line Items]
Customer Sales	$4,131	$4,652	$13,155	$14,841
Income (loss) from investees	26	48	31	116
Income (loss) from operations	-1,702	62	-1,671	242
Flat-rolled
Segment Reporting Information [Line Items]
Customer Sales	3,055	3,557	9,695	11,095
Income (loss) from investees	28	49	41	122
Income (loss) from operations	82	29	18	389
USSE
Segment Reporting Information [Line Items]
Customer Sales	644	764	2,207	2,417
Income (loss) from investees	0	0	0	0
Income (loss) from operations	-32	27	16	27
Tubular
Segment Reporting Information [Line Items]
Customer Sales	733	790	2,130	2,610
Income (loss) from investees	-1	-1	-7	-4
Income (loss) from operations	49	102	158	334
Total Reportable Segments
Segment Reporting Information [Line Items]
Customer Sales	4,432	5,111	14,032	16,122
Income (loss) from investees	27	48	34	118
Income (loss) from operations	99	158	192	750
Other Businesses
Segment Reporting Information [Line Items]
Customer Sales	58	40	216	270
Income (loss) from investees	-1	0	-3	-2
Income (loss) from operations	14	13	62	46
Reconciling Items and Eliminations
Segment Reporting Information [Line Items]
Customer Sales	-359	-499	-1,093	-1,551
Income (loss) from investees	0	0	0	0
Income (loss) from operations	-1,815	-109	-1,925	-554
Revenues from External Customers [Member]
Segment Reporting Information [Line Items]
Customer Sales	4,131	4,652	13,155	14,841
Revenues from External Customers [Member] | Flat-rolled
Segment Reporting Information [Line Items]
Customer Sales	2,731	3,142	8,710	9,798
Revenues from External Customers [Member] | USSE
Segment Reporting Information [Line Items]
Customer Sales	643	696	2,204	2,274
Revenues from External Customers [Member] | Tubular
Segment Reporting Information [Line Items]
Customer Sales	731	787	2,126	2,604
Revenues from External Customers [Member] | Total Reportable Segments
Segment Reporting Information [Line Items]
Customer Sales	4,105	4,625	13,040	14,676
Revenues from External Customers [Member] | Other Businesses
Segment Reporting Information [Line Items]
Customer Sales	26	27	115	165
Revenues from External Customers [Member] | Reconciling Items and Eliminations
Segment Reporting Information [Line Items]
Customer Sales	0	0	0	0
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Customer Sales	0	0	0	0
Intersegment Eliminations [Member] | Flat-rolled
Segment Reporting Information [Line Items]
Customer Sales	324	415	985	1,297
Intersegment Eliminations [Member] | USSE
Segment Reporting Information [Line Items]
Customer Sales	1	68	3	143
Intersegment Eliminations [Member] | Tubular
Segment Reporting Information [Line Items]
Customer Sales	2	3	4	6
Intersegment Eliminations [Member] | Total Reportable Segments
Segment Reporting Information [Line Items]
Customer Sales	327	486	992	1,446
Intersegment Eliminations [Member] | Other Businesses
Segment Reporting Information [Line Items]
Customer Sales	32	13	101	105
Intersegment Eliminations [Member] | Reconciling Items and Eliminations
Segment Reporting Information [Line Items]
Customer Sales	($359)	($499)	($1,093)	($1,551)

Segment_Information_Schedule_o

Segment Information - Schedule of Reconciling Items to Income (Loss) from Operations (Detail) (USD $)	3 Months Ended				9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Other items not allocated to segments:
Impairment of goodwill (Note 5)	($1,783)		$0		($1,783)		$0
Total reconciling items	-1,702		62		-1,671		242
Reconciling Items and Eliminations
Items not allocated to segments:
Postretirement benefit expense(a)	-55	[1]	-74	[1]	-165	[1]	-228	[1]
Other items not allocated to segments:
Impairment of goodwill (Note 5)	-1,783		0		-1,783		0
Supplier contract dispute settlement	23		0		23		0
Labor agreement lump sum payments(b)	0		-35	[2]	0		-35	[2]
Net loss on the sale of assets (Note 4)	0		0		0		-310
Property tax settlements	0		0		0		19
Total other items not allocated to segments	-1,760		-35		-1,760		-326
Total reconciling items	-1,815		-109		-1,925		-554
Labor Agreement lump sum payments per employee			$0
[1]	Consists of the net periodic benefit cost elements, other than service cost and amortization of prior service cost for active employees, associated with our pension, retiree health care and life insurance benefit plans.
[2]	Effective September 1, 2012, U. S. Steel and its U. S. Steel Tubular Products, Inc. subsidiary reached new labor agreements (the 2012 Labor Agreements) with the United Steel Workers (USW). The 2012 Labor Agreements provided for a $2,000 lump sum payment for each covered active USW member, which resulted in U. S. Steel recognizing a pretax charge of $35 million in the third quarter of 2012.

Segment_Information_Additional

Segment Information - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2013
	Segment
Segment Reporting [Abstract]
Number of reportable segments	3

Dispositions_Additional_Inform

Dispositions - Additional Information (Detail) (USD $)	0 Months Ended	1 Months Ended
	Jan. 31, 2012	Feb. 29, 2012
	U.S. Steel Serbia (USSS)	Birmingham Southern Railroad Company
Significant Acquisitions and Disposals [Line Items]
Proceeds from sale of USSS	$1
Additional payment received by USSK for intercompany balances owed by USSS	40,000,000
Gain (loss) on sale of assets	($399,000,000)	$89,000,000

Goodwill_and_Intangible_Assets2

Goodwill and Intangible Assets - Changes in Carrying Amount of Goodwill by Segment (Detail) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Goodwill [Roll Forward]
Goodwill beginning balance			$1,822
Goodwill from acquisitions			3
Impairment	-1,783	0	-1,783	0
Currency translation			-38
Goodwill ending balance	4		4
Flat-rolled
Goodwill [Roll Forward]
Goodwill beginning balance			984
Goodwill from acquisitions			0
Impairment			-946
Currency translation			-38
Goodwill ending balance	0		0
USSE
Goodwill [Roll Forward]
Goodwill beginning balance			4
Goodwill from acquisitions			0
Impairment			0
Currency translation			0
Goodwill ending balance	4		4
Tubular
Goodwill [Roll Forward]
Goodwill beginning balance			834
Goodwill from acquisitions			3
Impairment			-837
Currency translation			0
Goodwill ending balance	$0		$0

Goodwill_and_Intangible_Assets3

Goodwill and Intangible Assets - Amortizable Intangible Assets (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013	Sep. 30, 2013
In Millions, unless otherwise specified			Customer relationships	Customer relationships	Customer relationships	Customer relationships	Other	Other	Other	Other
					Minimum	Maximum			Minimum	Maximum
Finite-Lived Intangible Assets [Line Items]
Useful Lives					22 years	23 years			2 years	20 years
Gross Carrying Amount	$241	$243	$218	$221			$23	$22
Accumulated Amortization	73	65	61	54			12	11
Net Amount	$168	$178	$157	$167			$11	$11

Goodwill_and_Intangible_Assets4

Goodwill and Intangible Assets - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
	Unit		Unit
Indefinite-lived Intangible Assets [Line Items]
Number of reporting units that have a significant amount of goodwill	2		2
Acquisition of indefinite-lived intangible assets			$12	$0
Fair value of contingent consideration	24		24
Aggregate purchase price			36
Goodwill from acquisitions			3
Maximum potential liability for contingent consideration	53		53
Amortization expense	3	3	8	8
Expected amortization expense, remainder of current year	3		3
Expected amortization expense, for 2014	11		11
Expected amortization expense, for 2015	11		11
Expected amortization expense, for 2016	11		11
Expected amortization expense, for 2017	11		11
Goodwill, Impairment Loss	1,783	0	1,783	0
Goodwill (Note 5)	4		4		1,822
Fair Value Inputs, Long-term Revenue Growth Rate	3.00%
Fair Value Inputs, Discount Rate	10.00%
Use Rights [Member]
Indefinite-lived Intangible Assets [Line Items]
Carrying amount of acquired water rights with indefinite lives	75		75		75
Developed Technology Rights [Member]
Indefinite-lived Intangible Assets [Line Items]
Amount allocated to indefinite-lived intangible assets	33		33
Flat-rolled
Indefinite-lived Intangible Assets [Line Items]
Goodwill from acquisitions			0
Goodwill, Impairment Loss			946
Goodwill (Note 5)	0		0		984
Tubular
Indefinite-lived Intangible Assets [Line Items]
Goodwill from acquisitions			3
Goodwill, Impairment Loss			837
Goodwill (Note 5)	0		0		834
USSE
Indefinite-lived Intangible Assets [Line Items]
Goodwill from acquisitions			0
Goodwill, Impairment Loss			0
Goodwill (Note 5)	$4		$4		$4

Pensions_and_Other_Benefits_Ne

Pensions and Other Benefits - Net Periodic Benefit Costs (Detail) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$32	$29	$96	$88
Interest cost	100	117	303	350
Expected return on plan assets	-152	-154	-459	-460
Amortization of prior service cost	6	6	18	15
Amortization of actuarial net loss	92	88	275	264
Net periodic benefit cost, excluding below	78	86	233	257
Multiemployer plans	19	18	55	52
Settlement, termination and curtailment losses (gains)	3	0	3	-2
Net periodic benefit cost	100	104	291	307
Other Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	7	7	21	22
Interest cost	35	42	106	133
Expected return on plan assets	-33	-29	-98	-86
Amortization of prior service cost	-3	3	-10	14
Amortization of actuarial net loss	8	1	23	1
Net periodic benefit cost, excluding below	14	24	42	84
Multiemployer plans	0	0	0	0
Settlement, termination and curtailment losses (gains)	0	0	0	0
Net periodic benefit cost	$14	$24	$42	$84

Pensions_and_Other_Benefits_Ad

Pensions and Other Benefits - Additional Information (Detail) (USD $)	1 Months Ended	3 Months Ended		9 Months Ended			12 Months Ended	9 Months Ended
In Millions, unless otherwise specified	Jan. 31, 2013	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2013
						USSC Pension Plan	USSC Pension Plan	Steelworkers Pension Trust	Other Pension Plans, Defined Benefit	Unfunded Other Postretirement Benefit Plans	Defined Benefit Postretirement Health Coverage
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Contributions by Employer						$63		$56	$18
Cash contribution by employer to pension plans						140	140			188	10
Cash contribution by employer to defined contribution plans		11	10	33	31
Amount of voluntary pension funding authorized by the board of directors	300
Long-term earnings rate assumption				7.75%
Estimated future contribution in 2014		140		140
Estimated future contribution in 2015		$140		$140

Net_Interest_and_Other_Financi1

Net Interest and Other Financial Costs - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended		0 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Mar. 27, 2013	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2012
					2014 Senior Convertible Notes	2014 Senior Convertible Notes	Senior Notes Due Twenty Thirteen [Member]	Senior Notes Due Twenty Thirteen [Member]
Interest Expense [Line Items]
Net foreign currency remeasurement gains/losses	$3	$6	$9	$2
Charge for guarantee in unconsolidated equity method investment during the period	22		22
Charge associated with repurchases/redemptions of senior notes						34	18	18
Repurchased face amount of senior notes					$542	$542	$300	$300
Senior notes stated interest rate						4.00%
Debt instrument, due date						15-May-14		1-Jun-13

StockBased_Compensation_Plans_1

Stock-Based Compensation Plans - Summary of Awards Made under Plans (Detail) (USD $)	1 Months Ended				3 Months Ended
	31-May-13		31-May-12		Sep. 30, 2013
Executive Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares (a)	826,340	[1]	510,570	[1]
Fair Value (b)	$8.37	[2]	$11.93	[2]	$8.37
Non-executive Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares (a)	970,640	[1]	993,310	[1]
Fair Value (b)	$9.70	[2]	$11.93	[2]	$9.70
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares	1,033,210	[1]	910,011	[1]
Fair Value	$18.58	[2]	$22.28	[2]
Performance Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares	271,960	[1],[3]	328,780	[1],[3]
Fair Value	$21.26	[2],[3]	$25.26	[2],[3]
[1]	The share amounts shown in this table do not reflect an adjustment for estimated forfeitures.
[2]	er share weighted-average for all grants during the year.
[3]	The number of Performance Awards shown represents the target value of the award.

StockBased_Compensation_Plans_2

Stock-Based Compensation Plans - Black-Scholes Assumptions (Detail) (USD $)	1 Months Ended				3 Months Ended	1 Months Ended				3 Months Ended
	31-May-13		31-May-12		Sep. 30, 2013	31-May-13		31-May-12		Sep. 30, 2013	Sep. 30, 2012
	Executive Stock Options		Executive Stock Options		Executive Stock Options	Non-executive Stock Options		Non-executive Stock Options		Non-executive Stock Options	Executive and Non-Executive Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant date price per share of option award					$18.48					$18.64	$22.28
Exercise price per share of option award					$25					$18.64	$22.28
Expected annual dividends per share, at grant date					$0.20					$0.20	$0.20
Expected life in years					5 years					5 years	5 years
Expected volatility					66.00%					67.00%	68.00%
Risk-free interest rate					1.32%					1.05%	0.80%
Grant date fair value per share of unvested option awards as calculated from above	$8.37	[1]	$11.93	[1]	$8.37	$9.70	[1]	$11.93	[1]	$9.70	$11.93
[1]	er share weighted-average for all grants during the year.

StockBased_Compensation_Plans_3

Stock-Based Compensation Plans - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
In Millions, except Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate number of shares to be issued	15,450,000		15,450,000
Number of shares available for future grants	1,325,239		1,325,239
Stock-based compensation expense recognized	$9	$10	$28	$29
Unrecognized compensation costs related to non-vested stocks	$50		$50
Weighted average period for recognizing non-vested stock based compensation costs			1 year 3 months 18 days
Executive Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price per share of option award	$25
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation plans, award vesting period			3 years
Share-based compensation plans, award term			10 years
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation plans, award vesting period			3 years
Performance Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation plans, award vesting period			3 years
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%
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%

Income_Taxes_Additional_Inform

Income Taxes - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended			0 Months Ended	9 Months Ended					9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	Jan. 31, 2012	Sep. 30, 2012	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2013
						USSS	USSS	Domestic Country	Domestic Country	Foreign Country	Foreign Country	Slovakia	Slovakia	Goodwill [Member]
													Starting in 2013
Income Taxes [Line Items]
Provision for tax	$4,000,000	($27,000,000)	$14,000,000	$139,000,000			$0							$0
(Loss) income before income taxes	-1,787,000,000	17,000,000	-1,928,000,000	65,000,000
Goodwill, Impairment Loss	1,783,000,000	0	1,783,000,000	0
Gain (loss) on sale of assets						-399,000,000
Unrecognized tax benefits	85,000,000		85,000,000		85,000,000
Total amount of unrecognized tax benefits that, if recognized, would affect effective tax rate	65,000,000		65,000,000		65,000,000
Accrued liabilities, interest on unrecognized tax benefits	7,000,000		7,000,000		7,000,000
Unrecognized tax benefits, expected decrease in next 12 months	-8,000,000		-8,000,000
Net deferred tax asset								411,000,000	538,000,000	62,000,000	57,000,000
Deferred tax asset, valuation allowance										$1,184,000,000	$1,099,000,000
Statutory tax rate												19.00%	23.00%

Significant_Equity_Investments2

Significant Equity Investments - Summarized Unaudited Income Statement Information for Significant Equity Investments (Detail) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
Equity Method Investments and Joint Ventures [Abstract]
Net sales	$1,841	$1,982
Cost of sales	1,395	1,421
Operating income	399	533
Net income	382	521
Net income attributable to significant equity investments	$382	$521

Significant_Equity_Investments3

Significant Equity Investments - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Schedule of Equity Method Investments [Line Items]
Income (loss) from investees	$26	$48	$31	$116
Significant Equity Investments [Member]
Schedule of Equity Method Investments [Line Items]
Income (loss) from investees			$50	$121

Earnings_and_Dividends_Per_Com2

Earnings and Dividends Per Common Share - Computations for Basic and Diluted Income (Loss) Per Common Share from Continuing Operations (Detail) (USD $)	3 Months Ended		9 Months Ended
In Millions, except Share data in Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Net (loss) income attributable to United States Steel
Corporation shareholders	($1,791)	$44	($1,942)	($74)
Plus income effect of assumed conversion-interest on convertible notes	0	5	0	0
Net (loss) income after assumed conversion	($1,791)	$49	($1,942)	($74)
Weighted-average shares outstanding:
Basic	144,727	144,350	144,523	144,199
Effect of convertible notes	0	27,059	0	0
Effect of stock options, restricted stock units and performance awards	0	264	0	0
Adjusted weighted-average shares outstanding, diluted	144,727	171,673	144,523	144,199
Basic earnings per common share	($12.38)	$0.30	($13.44)	($0.51)
Diluted earnings per common share	($12.38)	$0.28	($13.44)	($0.51)

Earnings_and_Dividends_Per_Com3

Earnings and Dividends Per Common Share - Antidilutive Securities that were Not Included in Computations of Diluted Income (Loss) Per Common Share (Detail)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013		Sep. 30, 2012
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities	17,679	4,352	22,972		31,412
Securities granted under the 2005 Stock Incentive Plan
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities	7,621	4,352	7,621		4,353
Securities convertible under the Senior Convertible Notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities	10,058	0	15,351	[1]	27,059
[1]	On March 27, 2013, we repurchased approximately $542 million aggregate principal amount of our 4% Senior Convertible Notes due in 2014. If the repurchases had occurred on January 1, 2013, the antidilutive securities would be 10,058 for the nine months ended September 30, 2013.

Earnings_and_Dividends_Per_Com4

Earnings and Dividends Per Common Share - Antidilutive Securities that were Not Included in Computations of Diluted Income (Loss) Per Common Share (Parenthetical) (Detail) (USD $)	3 Months Ended		9 Months Ended		0 Months Ended	9 Months Ended
In Millions, except Share data in Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Mar. 27, 2013	Sep. 30, 2013
					2014 Senior Convertible Notes	2014 Senior Convertible Notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Repurchased face amount of senior notes					$542	$542
Senior notes stated interest rate						4.00%
Antidilutive Securities	17,679	4,352	22,972	31,412		10,058

Earnings_and_Dividends_Per_Com5

Earnings and Dividends Per Common Share - Additional Information (Detail) (USD $)	3 Months Ended
	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012
Earnings Per Share [Abstract]
Quarterly dividend per common share	$0.05	$0.05	$0.05	$0.05	$0.05	$0.05

Inventories_Detail

Inventories (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Millions, unless otherwise specified
Inventory Disclosure [Line Items]
Raw materials	$968	$945
Semi-finished products	877	883
Finished products	535	573
Supplies and sundry items	100	102
Total	$2,480	$2,503

Inventories_Additional_Informa

Inventories - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Inventory Disclosure [Line Items]
Percent of Last-in, First-out (LIFO) inventory to total inventory values	61.00%		61.00%		56.00%
Estimate in excess of current acquisition costs over stated inventory values	$1,100,000,000		$1,100,000,000		$1,000,000,000
Cost of sales increase/reduction, liquidations of LIFO inventories	3,000,000	5,000,000	3,000,000	16,000,000
Land held for residential or commercial development	$84,000,000		$84,000,000		$86,000,000

Derivative_Instruments_Additio

Derivative Instruments - Additional Information (Detail) (USD $)	Sep. 30, 2013
In Millions, unless otherwise specified
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Notional amount of forward contract	$333

Derivative_Instruments_Locatio

Derivative Instruments - Location and Amounts of Fair Values and Gains Or Losses Related to Derivatives in Financial Statements (Detail) (Foreign exchange forward contracts, Accounts payable, USD $)	Sep. 30, 2013	Dec. 31, 2012
In Millions, unless otherwise specified
Foreign exchange forward contracts | Accounts payable
Derivative [Line Items]
Fair value of derivatives	$9	$12

Derivative_Instruments_Locatio1

Derivative Instruments - Location and Amounts of Gains or Losses Related to Derivatives in Financial Statements (Detail) (Foreign Exchange Forward Contracts, Other financial costs, USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Foreign Exchange Forward Contracts | Other financial costs
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) related to derivatives	($11)	($12)	($7)	$1

Debt_Schedule_of_Debt_Detail

Debt - Schedule of Debt (Detail)

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Mar. 26, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Mar. 26, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

USD ($)

USD ($)

2037 Senior Notes

2037 Senior Notes

2022 Senior Notes

2022 Senior Notes

2021 Senior Notes

2021 Senior Notes

2021 Senior Notes

2020 Senior Notes

2020 Senior Notes

2018 Senior Notes

2018 Senior Notes

2017 Senior Notes

2017 Senior Notes

2019 Senior Convertible Notes

2019 Senior Convertible Notes

2019 Senior Convertible Notes

2014 Senior Convertible Notes

2014 Senior Convertible Notes

Province Note (C$150 million)

Province Note (C$150 million)

Province Note (C$150 million)

Province Note (C$150 million)

Environmental Revenue Bonds

Environmental Revenue Bonds

Environmental Revenue Bonds

Environmental Revenue Bonds

Recovery Zone Facility Bonds

Recovery Zone Facility Bonds

Fairfield Caster Lease

Fairfield Caster Lease

Other capital leases and all other obligations

Other capital leases and all other obligations

Other capital leases and all other obligations

Other capital leases and all other obligations

Amended Credit Agreement

Amended Credit Agreement

USSK Revolver

USSK Revolver

USSK credit facility

USSK credit facility

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

CAD

USD ($)

CAD

USD ($)

USD ($)

Minimum

Maximum

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

Minimum

Maximum

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

Debt Instrument [Line Items]

Debt instrument, face amount

$275,000,000

$316,000,000

150,000,000

150,000,000

Interest rate

6.65%

7.50%

6.88%

7.38%

7.00%

6.05%

2.75%

4.00%

1.00%

1.00%

6.75%

Interest rate %, minimum

5.38%

Interest rate %, maximum

6.88%

Interest rate description

Variable

Variable

Variable

Debt instrument, maturity date

2037

2022

2021

2020

2018

2017

2019

2014

2015

2015

2015

2042

2040

2022

2013

2014

2016

2016

2015

Debt and capital lease obligation

4,013,000,000

3,969,000,000

350,000,000

350,000,000

400,000,000

400,000,000

275,000,000

0

600,000,000

600,000,000

500,000,000

500,000,000

450,000,000

450,000,000

316,000,000

0

322,000,000

863,000,000

146,000,000

151,000,000

549,000,000

549,000,000

70,000,000

70,000,000

35,000,000

35,000,000

0

1,000,000

0

0

0

0

0

0

Less Province Note fair value adjustment

17,000,000

23,000,000

Less unamortized discount

56,000,000

8,000,000

49,000,000

Less short-term debt and long-term debt due within one year

322,000,000

2,000,000

Long-term debt

$3,618,000,000

$3,936,000,000

Debt_Redemption_Price_of_2021_

Debt - Redemption Price of 2021 Senior Notes as Percentage of Principal Amount Plus Accrued and Unpaid Interest to, but Excluding, Redemption Date (Detail)	Sep. 30, 2013
2017
Debt Instrument [Line Items]
2021 Senior Notes, redemption price	103.44%
2018
Debt Instrument [Line Items]
2021 Senior Notes, redemption price	101.72%
2019 and Thereafter
Debt Instrument [Line Items]
2021 Senior Notes, redemption price	100.00%

Debt_Eligible_Accounts_Receiva

Debt - Eligible Accounts Receivable and Receivables Sold to Third Party Conduits (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Millions, unless otherwise specified
Debt Disclosure [Abstract]
Balance of accounts receivable-net, eligible for sale to third-party conduits	$1,053	$1,127
Accounts receivable sold to third-party conduits	0	0
Balance included in Receivables on the balance sheet of U. S. Steel	$1,053	$1,127

Debt_Additional_Information_De

Debt - Additional Information (Detail)

0 Months Ended

1 Months Ended

9 Months Ended

0 Months Ended

3 Months Ended

9 Months Ended

1 Months Ended

3 Months Ended

0 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

0 Months Ended

Jul. 15, 2013

Sep. 30, 2013

Dec. 31, 2012

Mar. 31, 2013

Sep. 30, 2013

Sep. 30, 2013

Mar. 26, 2013

Jun. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Mar. 31, 2013

Jun. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Mar. 26, 2013

Sep. 30, 2013

Jun. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Jul. 15, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

USD ($)

USD ($)

Senior Convertible Notes

Senior Convertible Notes

Option Three

2021 Senior Notes

2021 Senior Notes

2021 Senior Notes

2021 Senior Notes

2014 Senior Convertible Notes

2014 Senior Convertible Notes

2014 Senior Convertible Notes

2014 Senior Convertible Notes

2019 Senior Convertible Notes

2019 Senior Convertible Notes

2019 Senior Convertible Notes

2019 Senior Convertible Notes

Amended Credit Agreement

Amended Credit Agreement

Amended Credit Agreement

Receivables purchase agreement [Member]

Receivables purchase agreement [Member]

Receivables purchase agreement [Member]

Receivables purchase agreement [Member]

Receivables purchase agreement [Member]

Change in control event

Fairfield Slab Caster

USSK Revolver

USSK Revolver

USSK Revolver

USSK credit facility

USSK credit facility

USSK credit facility

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

Covenant Requirement

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

EUR (€)

USD ($)

USD ($)

USD ($)

EUR (€)

USD ($)

USD ($)

Debt Instrument [Line Items]

Receivables Purchase Agreement Expiration Month Year

2016

Debt instrument, face amount

$275,000,000

$316,000,000

Interest rate %

6.88%

4.00%

2.75%

Debt instrument, due date

1-Apr-21

15-May-14

1-Apr-19

20-Jul-16

Net proceeds from offering

270,000,000

306,000,000

53,000,000

Underwriting discount and third party expenses

5,000,000

10,000,000

Debt instrument, payment frequency

semi-annually

semi-annually

Debt Instrument, Convertible, Conversion Ratio

39.5491

Dollar amount of Notes per conversion ratio

1,000

Senior Convertible Notes, conversion price per share (in dollars per share)

$25.29

Senior Convertible Notes, convertible into number of common stock shares (Based on the initial conversion rate)

12,507,403

Senior Convertible Notes, maximum amount that could be issued upon conversion

16,259,615

Repurchase of Senior Convertible Notes in whole or in part for cash in fundamental change, percentage of principal

100.00%

Senior Convertible Notes, unamortized discounts

56,000,000

8,000,000

49,000,000

Senior Convertible Note, net carrying amount

267,000,000

Senior convertible note, interest rate

6.20%

Repurchased face amount of senior notes

542,000,000

Aggregate principal amount, outstanding

4,013,000,000

3,969,000,000

275,000,000

0

322,000,000

863,000,000

316,000,000

0

0

0

0

0

0

0

Aggregate purchase price, including accrued and unpaid interest and fees

580,000,000

Premium on repurchase of senior notes

34,000,000

Amounts drawn on credit facility

0

0

Maximum borrowing capacity on credit facility

875,000,000

200,000,000

270,000,000

27,000,000

20,000,000

Credit Facility Expiration Month Year

2016

Fixed charge coverage ratio

1

Percentage of total aggregate commitments, upper range under financial covenant

10.00%

Credit Agreement, upper range of outstanding debt

87,500,000

Receivables Purchase Agreement, maximum amount of receivable eligible for sale

625,000,000

625,000,000

625,000,000

Receivables sold under receivables purchase agreement

0

0

0

Payments For Fees Related To Receivable Purchase Agreement

1,000,000

1,000,000

3,000,000

3,000,000

Amount reinvested from collection of eligible accounts receivable

0

1,175,000,000

Loss exposure

3,212,000,000

41,000,000

200,000,000

Available borrowing capacity

25,000,000

Customs and other guarantees outstanding

$2,000,000

Asset_Retirement_Obligations_C

Asset Retirement Obligations - Changes in Carrying Values of Asset Retirement Obligations (Detail) (USD $)	9 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of year	$33	$38
Additional obligations incurred	5	2
Obligations settled	-7	-9	[1]
Accretion expense	4	2
Balance at end of period	$35	$33
[1]	Includes $2 million as a result of the sale of USSS on January 31, 2012. See Note 4 for additional details.

Asset_Retirement_Obligations_C1

Asset Retirement Obligations - Changes in Carrying Values of Asset Retirement Obligations (Parenthetical) (Detail) (USD $)	9 Months Ended	12 Months Ended		0 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012		Jan. 31, 2012
				USSS
Reconciliation of Changes in Asset Retirement Obligations [Line Items]
Obligations settled	$7	$9	[1]	$2
[1]	Includes $2 million as a result of the sale of USSS on January 31, 2012. See Note 4 for additional details.

Fair_Value_of_Financial_Instru2

Fair Value of Financial Instruments - Financial Assets and Liabilities Not Carried at Fair Value (Detail) (USD $)	Sep. 30, 2013		Dec. 31, 2012
In Millions, unless otherwise specified
Financial assets:
Investments and long-term receivables (a)	$607		$609
Fair Value
Financial assets:
Investments and long-term receivables (a)	66	[1]	39	[1]
Financial liabilities:
Debt (b)	4,010	[2]	4,113	[2]
Carrying Amount
Financial assets:
Investments and long-term receivables (a)	66	[1]	39	[1]
Financial liabilities:
Debt (b)	$3,904	[2]	$3,902	[2]
[1]	Excludes equity method investments.
[2]	Excludes capital lease obligations.

Consolidated_Statement_of_Chan

Consolidated Statement of Changes in Equity (Detail) (USD $)	3 Months Ended		9 Months Ended												9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2012	Sep. 30, 2013	Dec. 31, 2012
					Comprehensive Income (Loss)	Comprehensive Income (Loss)	Retained Earnings	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss)	Common Stock	Common Stock	Common Stock	Common Stock	Treasury Stock	Treasury Stock	Paid-in Capital	Paid-in Capital	Non- Controlling Interest	Non- Controlling Interest	Non- Controlling Interest
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			$3,478	$3,501			$3,463	$3,616	($3,268)	($3,367)	$151	$151	$151	$151	($521)	($550)	$3,652	$3,650	$1	$1	$1
Comprehensive income:
Net (loss) income	-1,791	44	-1,942	-74	-1,942	-74	-1,942	-74
Other comprehensive income, net of tax:
Pension and other benefit adjustments	59	224	197	360	197	360			197	360
Currency translation adjustment	31	60	13	76	13	76			13	76
Issuance of conversion option in 2019 Senior Convertible Notes, net of tax			31														31
Employee stock plans			22	21											40	29	-18	-8
Dividends paid on common stock			-22	-22			-22	-22
Other			-2	1			-2												1
Ending balance	$1,775	$3,863	$1,775	$3,863	($1,732)	$362	$1,497	$3,520	($3,058)	($2,931)	$151	$151	$151	$151	($481)	($521)	$3,665	$3,642	$2	$1	$1

Reclassifications_from_Accumul2

Reclassifications from Accumulated Other Comprehensive Income - Other Comprehensive Income Activity Net of Tax (Detail) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013
Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	($3,268)	[1]
Other comprehensive income (loss) before reclassifications	0	[1]
Amounts reclassified from AOCI (b)	210	[1],[2]
Net current-period other comprehensive income	210	[1]
Ending Balance	-3,058	[1]
Pension and Other Benefit Items
Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	-3,613	[1]
Other comprehensive income (loss) before reclassifications	-13	[1]
Amounts reclassified from AOCI (b)	210	[1],[2]
Net current-period other comprehensive income	197	[1]
Ending Balance	-3,416	[1]
Foreign Currency Items
Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	345	[1]
Other comprehensive income (loss) before reclassifications	13	[1]
Amounts reclassified from AOCI (b)	0	[1],[2]
Net current-period other comprehensive income	13	[1]
Ending Balance	$358	[1]
[1]	All amounts are net of tax. Amounts in parentheses indicate debits.
[2]	See table below for further details.

Reclassifications_from_Accumul3

Reclassifications from Accumulated Other Comprehensive Income - Defined Benefit Plan In Other Comprehensive Income (Detail) (USD $)	3 Months Ended			9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012	Sep. 30, 2013		Sep. 30, 2012
Amortization of pension and other benefit items
(Loss) income before income taxes and noncontrolling interests	($1,787,000,000)		$17,000,000	($1,928,000,000)		$65,000,000
Tax benefit	-4,000,000		27,000,000	-14,000,000		-139,000,000
Net (loss) income	-1,791,000,000		44,000,000	-1,942,000,000		-74,000,000
Pension and Other Benefit Items | Reclassification out of Accumulated Other Comprehensive Income [Member]
Amortization of pension and other benefit items
Prior service costs	-3,000,000	[1],[2]		-8,000,000	[1],[2]
Actuarial gains/(losses)	-100,000,000	[1],[2]		-298,000,000	[1],[2]
(Loss) income before income taxes and noncontrolling interests	-103,000,000	[2]		-306,000,000	[2]
Tax benefit	29,000,000	[2]		96,000,000	[2]
Net (loss) income	($74,000,000)	[2]		($210,000,000)	[2]
[1]	These AOCI components are included in the computation of net periodic benefit cost (see Note 6 for additional details).
[2]	Amounts in parentheses indicate debits to income/loss.

Related_Party_Transactions_Add

Related Party Transactions - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Related Party Transaction [Line Items]
Net sales to related parties	$275	$342	$863	$1,003
Accounts payable to related parties	93		93		78
Outside processing services
Related Party Transaction [Line Items]
Purchases from related parties	18	16	53	44
Taconite pellets
Related Party Transaction [Line Items]
Purchases from related parties	63	84	180	204
PRO-TEC Coating Company
Related Party Transaction [Line Items]
Accounts payable to related parties	89		89		75
Other equity investees
Related Party Transaction [Line Items]
Accounts payable to related parties	$4		$4		$3

Contingencies_and_Commitments_1

Contingencies and Commitments - Changes in Accrued Liabilities for Remediation Activities (Detail) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013
Change in Accrued Liabilities for Remediation Activities [Roll Forward]
Beginning of period	$203
Accruals for environmental remediation deemed probable and reasonably estimable	5
Payments	-9
End of period	$199

Contingencies_and_Commitments_2

Contingencies and Commitments - Accrued Liabilities for Remediation Activities Included in Balance Sheet (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Millions, unless otherwise specified
Commitments and Contingencies Disclosure [Line Items]
Accounts payable, Deferred credits and other non-current liabilities	$199	$203
Accounts Payable
Commitments and Contingencies Disclosure [Line Items]
Accounts payable, Deferred credits and other non-current liabilities	17	21
Deferred credits and other noncurrent liabilities
Commitments and Contingencies Disclosure [Line Items]
Accounts payable, Deferred credits and other non-current liabilities	$182	$182

Contingencies_and_Commitments_3

Contingencies and Commitments - Payments for Contracts with Remaining Terms in Excess of One Year (Detail) (USD $)	Sep. 30, 2013
In Millions, unless otherwise specified
Commitments and Contingencies Disclosure [Abstract]
Remainder of 2013	$307
2014	806
2015	431
2016	332
2017	323
Later Years	1,728
Total	$3,927

Contingencies_and_Commitments_4

Contingencies and Commitments - Additional Information (Detail)

0 Months Ended

3 Months Ended

9 Months Ended

9 Months Ended

9 Months Ended

9 Months Ended

12 Months Ended

9 Months Ended

9 Months Ended

9 Months Ended

In Millions, unless otherwise specified

Aug. 02, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Facility

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

Randle Reef

Randle Reef

National Government

National Government

Provincial Government

Provincial Government

Local Sources

Local Sources

U. S. Steel Canada Inc.

U. S. Steel Canada Inc.

Minimum

Minimum

Maximum

Maximum

Asbestos Matters

Asbestos Matters

Asbestos Matters

Asbestos Matters

Asbestos Matters

Projects with Ongoing Study and Scope Development

Projects with Ongoing Study and Scope Development

Projects with Ongoing Study and Scope Development

Projects with Ongoing Study and Scope Development

Projects with Ongoing Study and Scope Development

Gary Works, Project with Defined Scope

Other Project with Defined Scope Greater Than or Equal to $5 Million

Other Project with Defined Scope Greater Than or Equal to $5 Million

Environmental Remediation Other Projects

Environmental Remediation Other Projects

Environmental Remediation Other Projects

Environmental Remediation Projects Less Than One Million

Environmental Remediation Projects Less Than One Million

Antitrust Class Actions

Surety Bonds

Restricted Cash To Fund Certain Capital Projects

T

T

USD ($)

CAD

Randle Reef

Randle Reef

Randle Reef

Randle Reef

Randle Reef

Randle Reef

Randle Reef

Randle Reef

USD ($)

Gateway Energy and Coke Company, LLC

USD ($)

Gateway Energy and Coke Company, LLC

USD ($)

USD ($)

Allege Suffering from Mesothelioma

Minimum

Maximum

USD ($)

Resource Conservation and Recovery Act (RCRA) Programs

Voluntary Remediation Program

Minimum

Maximum

USD ($)

USD ($)

Minimum

USD ($)

Minimum

Maximum

USD ($)

Maximum

Defendant

USD ($)

USD ($)

Micron

Micron

USD ($)

CAD

USD ($)

CAD

USD ($)

CAD

USD ($)

CAD

LegalMatter

Plaintiff

Plaintiff

Defendant

Defendant

Project

Project

Project

USD ($)

USD ($)

USD ($)

Project

USD ($)

USD ($)

USD ($)

T

Plaintiff

LegalMatter

Claim_Group

Loss Contingencies [Line Items]

Active cases brought against U.S. Steel

800

790

Number of plaintiffs involved

3,340

3,330

260

Number of defendants involved

50

100

8

Number of facilities that failed to meet certain environmental requirements

3

Number of claims pending in jurisdictions

2,560

Percentage of claims pending in jurisdictions

77.00%

Payment in settlement of claims

$6

$15

Cases resolved upon payment

175

190

Number of cases added and resulted in claims

185

285

Number of major groups

3

Expenses related to remediation included in cost of sales

1

2

5

11

Projected percentage remediation costs may exceed accrued liabilities

20.00%

40.00%

Environmental remediation projects

6

4

1

6

Accrued liabilities for remediation activities

199

199

203

23

57

64

5

13

1

5

8

1

Environment exit costs, possible additional loss

45

75

Accrued liabilities for post-closure site monitoring and other costs

28

28

Accrued liability for administrative and legal costs

6

6

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

3 years

Capital expenditures

36

37

Percent reduction in free allocation of emissions

12.00%

Minimum annual increment in GHG emission due to modifications to existing permits subject to Title V and PSD requirement if only project significantly increases emissions of at least one non-GHG pollutant

75,000

75,000

Minimum annual emission of new sources subject to PSD and Title V requirement

100,000

100,000

NAAQS micron particulate matter in revision process

2.5

2.5

Estimated capital expenditures of complying with BAT over 2013 to 2016 period

300

400

Financial assurance guarantees, maximum

29

29

168

Liability related to a guarantee of an unconsolidated equity investment

22

22

Regulatory agencies estimate expenditures amount

117

120

Committed contribution

39

40

39

40

39

40

Contributions made during the period, hot rolled steel

11,000

11,000

Contributions made during the period, cash

2

2

Expected date of committed contribution

2014

2014

Liability accrued related to committed contributions

10

Residual value of equipment

16

16

Restricted cash

142

142

181

50

Restricted cash current

1

1

5

Contract commitments to acquire property, plant and equipment

235

235

Unconditional purchase obligation term

2 years

15 years

Percentage of purchase obligation

90.00%

105.00%

Maximum default payment on termination of agreement

250

250

Total payment under take-or-pay contracts

$115

$180

$410

$550

Subsequent_Event_Details

Subsequent Event (Details) (USD $)	1 Months Ended
In Millions, unless otherwise specified	Oct. 25, 2013
Subsequent Events [Abstract]
Impairment, non-cash charge expected to be recorded in the fourth quarter of 2013	$225