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Stock Option Plans (Tables)
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9 Months Ended |
12 Months Ended |
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Sep. 30, 2013
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Dec. 31, 2012
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| Disclosure Of Compensation Related Costs Sharebased Payments [Abstract] |
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| Summary of Assumptions Used in Pricing Model |
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The assumptions used in the
Black-Scholes option pricing model for the years ended
December 31, 2012 and 2011 are set forth below:
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2012 |
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2011 |
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Valuation
assumptions
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Expected dividend yield
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0% |
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0% |
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Expected volatility
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71%—76% |
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68%—72% |
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Expected term (years)
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6.00 |
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5.37— 6.23 |
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Risk-free interest rate
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0.80%—1.10% |
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1.34%—2.51% |
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| Schedule of Stock Option Activity |
Stock option activity under the
Company’s award plans during the period indicated is as
follows:
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Number
of
shares
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Weighted
average
exercise
price
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Weighted
average
remaining
contractual
term
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Balances at December 31,
2012
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2,313,526 |
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$ |
5.90 |
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7.87 |
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Granted
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764,209 |
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11.07 |
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Exercised
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(17,649 |
) |
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(3.10 |
) |
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Forfeited
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(325,604 |
) |
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(6.94 |
) |
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Expired
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(36,865 |
) |
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(5.15 |
) |
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Balances at September 30,
2013
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2,697,617 |
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7.26 |
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7.68 |
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Vested at September 30,
2013
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992,112 |
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4.67 |
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5.79 |
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Vested and Expected to Vest at
September 30, 2013(1)
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2,434,816 |
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6.20 |
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6.91 |
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| (1) |
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The number of stock options expected to vest takes into
account an estimate of expected forfeitures. |
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Stock option activity during the years
indicated is as follows:
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Number of
shares |
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Weighted
average
exercise
price |
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Weighted
average
remaining
contractual
term |
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Balances at December 31,
2010
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1,448,145 |
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2.71 |
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6.99 |
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Granted
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2,429,684 |
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6.48 |
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Exercised
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(75,840 |
) |
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(2.43 |
) |
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Forfeited
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(145,214 |
) |
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(3.34 |
) |
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Expired
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(42,245 |
) |
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(2.94 |
) |
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Balances at December 31,
2011
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3,614,530 |
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5.22 |
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6.67 |
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Granted
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548,571 |
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7.12 |
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Exercised
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(194,570 |
) |
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(2.43 |
) |
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Forfeited
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(1,210,857 |
) |
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(6.30 |
) |
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Expired
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(444,148 |
) |
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(2.29 |
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Balances at December 31,
2012
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2,313,526 |
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5.90 |
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7.87 |
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Exercisable at December 31,
2012
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808,633 |
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4.06 |
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6.43 |
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Vested and Expected to
Vest at December 31, 2012(1)
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2,194,790 |
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5.85 |
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7.83 |
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| (1) |
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The number of stock options expected to vest takes into account
an estimate of expected forfeitures. |
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| Summary of Additional Information About Stock Options |
|
The following table summarizes
additional information about stock options outstanding as of
December 31, 2012:
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| Options
outstanding |
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Options
exercisable |
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| Exercise price |
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Number of
options |
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Weighted
average
remaining
life (years) |
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Aggregate
intrinsic
value |
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Number of
options |
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Weighted
average
remaining
life
(years) |
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Aggregate
intrinsic
value |
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$0.38
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57,264 |
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8.07 |
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$ |
385 |
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57,264 |
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8.07 |
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$ |
385 |
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$1.34
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106,777 |
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3.10 |
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617 |
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106,777 |
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3.10 |
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617 |
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$1.92
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23,143 |
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4.25 |
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120 |
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23,143 |
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4.25 |
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120 |
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$2.74
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186,286 |
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4.62 |
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815 |
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186,286 |
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4.62 |
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815 |
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$3.29
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183,442 |
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6.77 |
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703 |
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126,014 |
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6.72 |
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483 |
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$5.91
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169,857 |
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7.64 |
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205 |
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42,571 |
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7.59 |
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51 |
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$7.12
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1,586,757 |
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8.77 |
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— |
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266,578 |
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8.53 |
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— |
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2,313,526 |
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7.87 |
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$ |
2,845 |
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808,633 |
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6.43 |
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$ |
2,471 |
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The following table summarizes
additional information about stock options outstanding as of
December 31, 2011:
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| Options
outstanding |
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Options
exercisable |
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| Exercise price |
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Number of
options |
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Weighted
average
remaining
life (years) |
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Aggregate
intrinsic
value |
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Number of
options |
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Weighted
average
remaining
life
(years) |
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Aggregate
intrinsic
value |
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$0.38
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145,406 |
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9.07 |
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$ |
978 |
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145,406 |
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9.07 |
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$ |
978 |
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$1.34
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257,680 |
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4.10 |
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1,489 |
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257,680 |
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4.10 |
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1,489 |
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$1.68
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58,286 |
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2.84 |
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317 |
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58,286 |
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2.84 |
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317 |
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$1.92
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23,143 |
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5.26 |
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120 |
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23,143 |
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5.26 |
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120 |
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$1.96
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3,015 |
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9.07 |
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16 |
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3,015 |
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9.07 |
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16 |
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$2.74
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312,572 |
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5.54 |
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1,368 |
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307,572 |
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5.54 |
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1,346 |
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$3.29
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564,286 |
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7.50 |
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2,163 |
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212,929 |
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7.35 |
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|
816 |
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$5.91
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363,142 |
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8.41 |
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438 |
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— |
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— |
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— |
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$7.12
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1,887,000 |
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6.58 |
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— |
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— |
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— |
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— |
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3,614,530 |
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6.67 |
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$ |
6,889 |
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1,008,031 |
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5.91 |
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$ |
5,082 |
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