Stock-Based Compensation Plans - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified
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3 Months Ended |
Mar. 31, 2015
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Mar. 31, 2014
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Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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Aggregate number of shares to be issued |
21,250,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized |
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Number of shares available for future grants |
1,262,031us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant |
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Stock-based compensation expense recognized |
$ 11us-gaap_AllocatedShareBasedCompensationExpense |
$ 9us-gaap_AllocatedShareBasedCompensationExpense |
Unrecognized compensation costs related to non-vested stocks |
$ 62us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized |
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Weighted average period for recognizing non-vested stock based compensation costs |
1 year 2 months |
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Stock Options |
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Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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Share-based compensation plans, award vesting period |
3 years |
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Shares - Stock Options |
1,067,190us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember |
0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember |
Share-based compensation plans, award term |
10 years |
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Restricted Stock Units |
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Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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Share-based compensation plans, award vesting period |
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3 years |
Shares - Other than Stock Options |
765,750us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember |
0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember |
Total Shareholder Return (TSR) Performance Awards |
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Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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Share-based compensation plans, award vesting period |
3 years |
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Shares - Other than Stock Options |
273,560us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = x_TotalStockholdersReturnTSRPerformanceBasedRestrictedStockMember |
279,570us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = x_TotalStockholdersReturnTSRPerformanceBasedRestrictedStockMember |
Total Shareholder Return (TSR) Performance Awards | Minimum |
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Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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Vesting of performance awards as percentage to target award |
0.00%x_ShareBasedCompensationArrangementByShareBasedPaymentAwardTargetAward / us-gaap_AwardTypeAxis = x_TotalStockholdersReturnTSRPerformanceBasedRestrictedStockMember / us-gaap_RangeAxis = us-gaap_MinimumMember |
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Total Shareholder Return (TSR) Performance Awards | Maximum |
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Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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Vesting of performance awards as percentage to target award |
200.00%x_ShareBasedCompensationArrangementByShareBasedPaymentAwardTargetAward / us-gaap_AwardTypeAxis = x_TotalStockholdersReturnTSRPerformanceBasedRestrictedStockMember / us-gaap_RangeAxis = us-gaap_MaximumMember |
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Return On Capital Employed (ROCE) Performance Awards |
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Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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Share-based compensation plans, award vesting period |
3 years |
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Performance Period Weighting Year 1 |
20.00%x_PerformancePeriodWeightingYearOne / us-gaap_AwardTypeAxis = x_ReturnOnCapitalEmployedROCEPerformanceBasedRestrictedStockMember |
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Performance Period Weighting Year 2 |
30.00%x_PerformancePeriodWeightingYearTwo / us-gaap_AwardTypeAxis = x_ReturnOnCapitalEmployedROCEPerformanceBasedRestrictedStockMember |
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Performance Period Weighting Year 3 |
50.00%x_PerformancePeriodWeightingYearThree / us-gaap_AwardTypeAxis = x_ReturnOnCapitalEmployedROCEPerformanceBasedRestrictedStockMember |
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Shares - Other than Stock Options |
0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = x_ReturnOnCapitalEmployedROCEPerformanceBasedRestrictedStockMember |
259,280us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = x_ReturnOnCapitalEmployedROCEPerformanceBasedRestrictedStockMember |
Return On Capital Employed (ROCE) Performance Awards | Threshold |
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Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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Vesting of performance awards as percentage to target award |
50.00%x_ShareBasedCompensationArrangementByShareBasedPaymentAwardTargetAward / us-gaap_AwardTypeAxis = x_ReturnOnCapitalEmployedROCEPerformanceBasedRestrictedStockMember / us-gaap_RangeAxis = x_ThresholdMember |
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Return On Capital Employed (ROCE) Performance Awards | Target |
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Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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Vesting of performance awards as percentage to target award |
100.00%x_ShareBasedCompensationArrangementByShareBasedPaymentAwardTargetAward / us-gaap_AwardTypeAxis = x_ReturnOnCapitalEmployedROCEPerformanceBasedRestrictedStockMember / us-gaap_RangeAxis = x_TargetMember |
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Return On Capital Employed (ROCE) Performance Awards | Minimum |
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Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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Vesting of performance awards as percentage to target award |
0.00%x_ShareBasedCompensationArrangementByShareBasedPaymentAwardTargetAward / us-gaap_AwardTypeAxis = x_ReturnOnCapitalEmployedROCEPerformanceBasedRestrictedStockMember / us-gaap_RangeAxis = us-gaap_MinimumMember |
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Return On Capital Employed (ROCE) Performance Awards | Maximum |
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Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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Vesting of performance awards as percentage to target award |
200.00%x_ShareBasedCompensationArrangementByShareBasedPaymentAwardTargetAward / us-gaap_AwardTypeAxis = x_ReturnOnCapitalEmployedROCEPerformanceBasedRestrictedStockMember / us-gaap_RangeAxis = us-gaap_MaximumMember |
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