|
SHARE-BASED COMPENSATION Schedule of Stock Options Valuation Assumptions (Details) (USD $)
|
12 Months Ended | |
|---|---|---|
|
Dec. 31, 2014
|
Dec. 31, 2013
|
|
| Disclosure of Compensation Related Costs, Share-based Payments [Abstract] | ||
| Risk free interest rate | 1.75%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate | 0.81%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate |
| Expected life (years) | 5 years | 5 years |
| Volatility | 39.62%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate | 50.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate |
| Dividend yield | 0.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate | 0.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate |
| Weighted average exercise price of options granted (per option) | $ 29.24us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExercisePrice | $ 19.05us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExercisePrice |
| Fair value of stock options granted | $ 10.86era_SharebasedCompensationArrangementbySharebasedPaymentAwardOptionsGrantsinPeriodWeightedAverageGrantDateFairValueIncludingConvertedInstruments | $ 7.87era_SharebasedCompensationArrangementbySharebasedPaymentAwardOptionsGrantsinPeriodWeightedAverageGrantDateFairValueIncludingConvertedInstruments |
| X | ||||||||||
|
- Definition
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value, Including Converted Instruments No definition available.
|
| X | ||||||||||
|
- Details
|
| X | ||||||||||
|
- Definition
Agreed-upon price for the exchange of the underlying asset relating to the share-based payment award. No definition available.
|
| X | ||||||||||
|
- 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
|
| X | ||||||||||
|
- 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
|
| X | ||||||||||
|
- Definition
The estimated measure of the 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. Reference 1: http://www.xbrl.org/2003/role/presentationRef
|
| X | ||||||||||
|
- Definition
The risk-free interest rate assumption that is used in valuing an option on its own shares. Reference 1: http://www.xbrl.org/2003/role/presentationRef
|