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Stock-based compensation (Tables)
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Mar. 31, 2015
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| Disclosure of Compensation Related Costs, Share-based Payments [Abstract] | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Schedule of Assumptions Used to Estimate Fair Value of Stock Option Award Using Black-Scholes Valuation Model |
The fair value of each option grant is estimated on the date of grant using the Black-Scholes model with the following weighted-average assumptions:
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| Summary of Stock Option Activity Under Stock Option and Incentive Plans |
A summary of the status of stock option awards and changes during the three months ended March 31, 2015 are presented below:
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- Details
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- Definition
Tabular disclosure of the number and weighted-average exercise prices (or conversion ratios) for share options (or share units) that were outstanding at the beginning and end of the year, vested and expected to vest, exercisable or convertible at the end of the year, and the number of share options or share units that were granted, exercised or converted, forfeited, and expired during the year. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition
Tabular disclosure of the significant assumptions used during the year to estimate the fair value of stock options, including, but not limited to: (a) expected term of share options and similar instruments, (b) expected volatility of the entity's shares, (c) expected dividends, (d) risk-free rate(s), and (e) discount for post-vesting restrictions. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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