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Additional Paid-In Capital | 12 Months Ended
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Dec. 31, 2012
Additional Paid-In Capital [Abstract] |
Additional Paid-In Capital | 9. Additional Paid-in Capital
|  | Warrants |  |  | Stock options and RSUs |  |  | Compensation options |  |  | Other paid-in capital |  |  | Total additional paid-in capital
As of December 31, 2010 | $ | 10,721 |  | $ | 4,695 |  | $ | - |  | $ | 7,565 |  | $ | 22,981
Convertible notes broker warrants |  | (336) |  |  | - |  |  | - |  |  | 336 |  |  | -
Warrants exercised |  | (97) |  |  | - |  |  | - |  |  | - |  |  | (97)
Compensation options issued |  | - |  |  | - |  |  | 588 |  |  | - |  |  | 588
Stock options exercised |  | - |  |  | (430) |  |  | - |  |  | - |  |  | (430)
Stock options expired |  | - |  |  | (828) |  |  | - |  |  | 828 |  |  | -
Stock options amortization |  | - |  |  | 1,496 |  |  | - |  |  | - |  |  | 1,496
Restricted stock units exercised |  | - |  |  | (392) |  |  | - |  |  | - |  |  | (392)
Restricted stock units expensed |  | - |  |  | 524 |  |  | - |  |  | - |  |  | 524
As of December 31, 2011 |  | 10,288 |  |  | 5,065 |  |  | 588 |  |  | 8,729 |  |  | 24,670
Warrants exercised |  | (601) |  |  | - |  |  | - |  |  | 601 |  |  | -
Warrants issued |  | 3,260 |  |  | - |  |  | - |  |  | - |  |  | 3,260
Warrants expired |  | (11) |  |  | - |  |  | - |  |  | 11 |  |  | -
Stock options amortization |  | - |  |  | 1,081 |  |  | - |  |  | - |  |  | 1,081
Stock options exercised |  | - |  |  | (50) |  |  | - |  |  | 50 |  |  | -
Stock options expired |  | - |  |  | (1,585) |  |  | - |  |  | 1,585 |  |  | -
Restricted stock units expensed |  | - |  |  | 3,144 |  |  | - |  |  | - |  |  | 3,144
Compensation options exercised |  | - |  |  | - |  |  | (294) |  |  | 294 |  |  | -
As of December 31, 2012 | $ | 12,936 |  | $ | 7,655 |  | $ | 294 |  | $ | 11,270 |  | $ | 32,155
Warrants Warrant activity is summarized in the following table:
|  | Warrants outstanding |  | Valuation |  | Weighted average exercise price per share |  | Weighted average remaining life (yrs.) |  | Intrinsic value
As of December 31, 2010 |  | 16,138,480 | $ | 10,721 | $ | 3.48 |  | 4.6 | $ | 57
Convertible notes broker warrants expired |  | (200,000) |  | (336) |  |  |  |  |  |
Exercised |  | (88,242) |  | (97) |  |  |  |  |  |
As of December 31, 2011 |  | 15,850,238 |  | 10,288 | $ | 3.91 |  | 3.7 | $ | 485
Exercised |  | (619,565) |  | (601) |  |  |  |  |  |
Expired |  | (10,871) |  | (11) |  |  |  |  |  |
Issued (Note 8) |  | 4,757,941 |  | 3,260 |  |  |  |  |  |
As of December 31, 2012 |  | 19,977,743 | $ | 12,936 | $ | 4.25 |  | 2.6 | $ | -
The 19,977,743 outstanding warrants expire in the following time frames: 2,666,666 expire July 2014, 2,091,275 expire December 2014, and 15,219,802 expire in October 2015. The fair value of warrants issued during 2012 was estimated at the issue date using the Black-Scholes Merton fair value model adjusted to relative fair value using the following assumptions:
Expected volatility |  | 63.70% | - | 67.50%
Risk-free interest rate |  | 0.24% | - | 0.26%
Expected life (years) |  | 2
Dividend yield |  | N/A
Compensation Options
|  | Compensation options outstanding |  |  | Valuation |  |  | Weighted average exercise price per share |  | Expiry date |  | Weighted average remaining life (yrs.)
As of December 31, 2010 |  | - |  | $ | - |  | $ | - |  |  |  |
Issued |  | 450,000 |  |  | 588 |  |  | 3.30 |  | April 2013 |  | 2.0
As of December 31, 2011 |  | 450,000 |  |  | 588 |  |  | 3.30 |  | April 2013 |  | 1.3
Exercised |  | (225,000) |  |  | (294) |  |  |  |  |  |  |
As of December 31, 2012 |  | 225,000 |  | $ | 294 |  | $ | 3.30 |  | April 2013 |  | 0.3
Stock-Based Compensation Under our Stock Option Plan (the “Plan”) and our Long-Term Equity Incentive Plan (the “LTIP”), we may grant options and/or restricted stock units (“RSUs”) or restricted stock awards (“RSAs”) to our directors, officers, employees and consultants. The combined maximum number of our Common Shares that may be reserved for issuance under the Plan and the LTIP is a variable number equal to 10% of the issued and outstanding Common Shares on a non-diluted basis. Options under the Plan are granted from time to time at the discretion of the Board of Directors of the Company (“Board”), with vesting periods and other terms as determined by the Board. The LTIP is administered by the Board, which can delegate the administration to the Compensation Committee of the Board or to such other officers and employees of Vista as designated by the Board. Stock-based compensation expense for the years ended December 31, 2012, 2011 and 2010 is as follows:
|  | Year ended December 31,
|  | 2012 |  | 2011 |  | 2010
Stock options | $ | 1,081 | $ | 1,496 | $ | 382
Restricted stock units |  | 3,144 |  | 524 |  | 126
| $ | 4,225 | $ | 2,020 | $ | 508
As of December 31, 2012, stock options and RSUs had unrecogni zed compensation expense of $314 and $3,589, respectively, which is expected to be recognized over a weighted average period of 0.74 and 1.76 years, respectively. Stock Options A summary of option activity under the Plan as of December 31, 2012 and 2011 and changes during the period then ended is set forth in the following table:
|  | Number of options |  | Weighted average exercise price per option |  | Weighted average remaining contractual term |  | Aggregate intrinsic value
Outstanding - December 31, 2010 |  | 2,588,661 | $ | 3.55 |  | 2.90 | $ | 463
Granted |  | 1,246,000 |  | 3.04 |  |  |  |
Exercised |  | (354,984) |  | 2.48 |  |  |  |
Cancelled |  | (85,500) |  | 3.44 |  |  |  |
Expired/Forfeited |  | (199,177) |  | 6.90 |  |  |  |
Outstanding - December 31, 2011 |  | 3,195,000 |  | 3.27 |  | 2.73 |  | 1,039
Granted |  | 600,000 |  | 2.97 |  |  |  |
Exercised |  | (32,500) |  | 2.90 |  |  |  |
Expired |  | (660,000) |  | 5.19 |  |  |  |
Outstanding - December 31, 2012 |  | 3,102,500 | $ | 2.80 |  | 2.68 | $ | 637
Exercisable - December 31, 2012 |  | 2,802,500 | $ | 2.79 |  | 2.49 | $ | 626
A summary of our unvested stock options as of December 31, 2012 and 2011 and changes during the period then ended is set forth in the following table:
|  |  |  |  |  | Number of options |  | Weighted average grant-date fair value per option |
Unvested - December 31, 2010 |  |  |  |  |  | 82,500 | $ | 1.36 |
Granted |  |  |  |  |  | 1,246,000 |  | 1.60 |
Vested |  |  |  |  |  | (693,000) |  | 1.57 |
Forfeited |  |  |  |  |  | (38,000) |  | 1.51 |
Unvested - December 31, 2011 |  |  |  |  |  | 597,500 |  | 1.60 |
Granted |  |  |  |  |  | 600,000 |  | 1.47 |
Vested |  |  |  |  |  | (897,000) |  | 1.56 |
Unvested - December 31, 2012 |  |  |  |  |  | 300,000 | $ | 1.47 |
The fair value of stock options granted to employees, directors and consultants was estimated at the grant date using the Hull-White Trinomial lattice option pricing model using the following assumptions:
|  |  |  |  | Years ended December 31,
|  |  | 2012 |  | 2011 |  | 2010
Expected volatility |  |  | 81.69% | - | 83.67% |  | 83.40% | - | 83.86% |  | 81.86% | - | 82.88%
Risk-free interest rate |  |  | 0.77% | - | 0.88% |  | 0.88% | - | 1.60% |  | 1.51% | - | 2.88%
Expected life (years) |  |  | 5 |  | 5 |  | 5
Dividend yield |  |  | N/A |  | N/A |  | N/A
Option pricing models require the input of highly subjective assumptions, including the expected price volatility. Expected price volatility is based on the historical volatility of our Common Shares. Changes in the subjective input assumptions can materially affect the fair value estimate. The expected term of the options granted is derived from the output of the option pricing model and represents the period of time that the options granted are expected to be outstanding. The risk-free rate for the periods within the contractual term of the option is based on the U.S. Treasury yield curve in effect at the date of grant. Restricted Stock Units The following table summarizes the RSU activity under the LTIP as of December 31, 2012 and 2011 and changes during the years then ended is set forth in the following table:
|  | Number of units |  | Weighted average grant-date fair value per RSU
Unvested - December 31, 2010 |  | 175,500 | $ | 2.37
Forfeited |  | (10,000) |  | 2.37
Vested |  | (165,500) |  | 2.37
Granted |  | 960,000 |  | 3.84
Unvested - December 31, 2011 |  | 960,000 |  | 3.84
Cancelled |  | (107,832) |  | 3.07
Granted |  | 1,142,339 |  | 3.20
Unvested - December 31 , 2012 |  | 1,994,507 | $ | 3.52
A portion of the RSU awards vest on a fixed future date provided the recipient continues to be affiliated with Vista on that date. Other RSU awards vest subject to certain performance criteria, including the accomplishment of certain corporate objectives and the Company’s share price performance. The vesting of all RSUs is at least one year.

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- Definition The entire disclosure of the components pertaining to additional paid in capital related to options and warrants. + References No definition available. + Details
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