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Shareholders' Equity and Capital Stock - assumptions (Details)
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12 Months Ended | ||
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Dec. 31, 2014
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Dec. 31, 2013
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Dec. 31, 2012
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||
| Expected volatility, Minimum | 61.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMinimum | 61.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMinimum | 63.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMinimum |
| Expected volatility, Maximum | 66.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMaximum | 66.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMaximum | 78.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMaximum |
| Risk-free interest rate, Minimum | 1.10%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMinimum | 0.90%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMinimum | 1.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMinimum |
| Risk-free interest rate, Maximum | 1.40%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMaximum | 1.40%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMaximum | 1.30%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMaximum |
| Expected dividend rate | 0.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate | 0.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate | 0.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate |
| Restricted Stock Units (Rsus) [Member] | |||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||
| Forfeiture rate (as a percent) |
8.10%urg_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsForfeitureRate / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember |
7.70%urg_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsForfeitureRate / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember |
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| Warrants | |||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||
| Expected award life (in years) | 1 year 6 months | ||
| Forfeiture rate (as a percent) |
0.00%urg_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsForfeitureRate / us-gaap_AwardTypeAxis = us-gaap_WarrantMember |
0.00%urg_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsForfeitureRate / us-gaap_AwardTypeAxis = us-gaap_WarrantMember |
0.00%urg_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsForfeitureRate / us-gaap_AwardTypeAxis = us-gaap_WarrantMember |
| Maximum | Employee Stock Option [Member] | |||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||
| Expected award life (in years) | 3 years 6 months 22 days | 3 years 6 months 4 days | 3 years 4 months 13 days |
| Forfeiture rate (as a percent) |
4.70%urg_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsForfeitureRate / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_RangeAxis = us-gaap_MaximumMember |
4.40%urg_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsForfeitureRate / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_RangeAxis = us-gaap_MaximumMember |
4.80%urg_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsForfeitureRate / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_RangeAxis = us-gaap_MaximumMember |
| Maximum | Restricted Stock Units (Rsus) [Member] | |||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||
| Forfeiture rate (as a percent) |
22.30%urg_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsForfeitureRate / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember / us-gaap_RangeAxis = us-gaap_MaximumMember |
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| Maximum | Warrants | |||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||
| Expected award life (in years) | 3 years | ||
| Minimum | Employee Stock Option [Member] | |||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||
| Expected award life (in years) | 3 years 5 months 27 days | 3 years 4 months 28 days | 3 years 3 months 15 days |
| Forfeiture rate (as a percent) |
4.50%urg_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsForfeitureRate / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_RangeAxis = us-gaap_MinimumMember |
4.20%urg_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsForfeitureRate / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_RangeAxis = us-gaap_MinimumMember |
4.60%urg_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsForfeitureRate / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_RangeAxis = us-gaap_MinimumMember |
| Minimum | Restricted Stock Units (Rsus) [Member] | |||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||
| Forfeiture rate (as a percent) |
12.50%urg_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsForfeitureRate / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember / us-gaap_RangeAxis = us-gaap_MinimumMember |
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| Minimum | Warrants | |||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||
| Expected award life (in years) | 0 years | 1 year 6 months | |
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- Definition
The forfeiture rate assumption that is used in valuing share-based compensation awards. No definition available.
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- Definition
The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition
Expected term of share-based compensation awards, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition
The estimated measure of the maximum percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period. No definition available.
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- Definition
The estimated measure of the minimum percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period. No definition available.
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- Definition
The maximum risk-free interest rate assumption that is used in valuing an option on its own shares. No definition available.
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- Definition
The minimum risk-free interest rate assumption that is used in valuing an option on its own shares. No definition available.
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