Stock-Based Compensation (Tables)
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6 Months Ended |
Jun. 30, 2018 |
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| Disclosure of Compensation Related Costs, Share-based Payments [Abstract] |
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| Schedule of Compensation Expense |
The following table summarizes stock-based compensation expense recognized for the periods presented: | | | | | | | | | | | | | | | | | | For the Three Months Ended June 30, | | For the Six Months Ended June 30, | (in thousands) | 2018 | | 2017 | | 2018 | | 2017 | Restricted stock awards | $ | 1,989 |
| | $ | 1,018 |
| | $ | 3,764 |
| | $ | 1,874 |
| Stock option awards | 2,310 |
| | 1,967 |
| | 4,516 |
| | 3,721 |
| Performance stock units | 356 |
| | — |
| | 708 |
| | — |
| Total stock-based compensation expense | $ | 4,655 |
| | $ | 2,985 |
| | $ | 8,988 |
| | $ | 5,595 |
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| Nonvested Restricted Stock Shares Activity |
The following table provides information about restricted stock awards outstanding during the six months ended June 30, 2018: | | | | | | | | | Awards | | Weighted Average Grant Date Fair Value | Unvested balance as of December 31, 2017 | 1,009,716 |
| | $ | 17.64 |
| Granted | 221,505 |
| | 18.87 |
| Vested | (75,272 | ) | | 18.36 |
| Forfeited | (43,298 | ) | | 17.01 |
| Unvested balance as of June 30, 2018 | 1,112,651 |
| | 17.86 |
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| Summary of Stock Option Valuation Inputs |
The following table summarizes the assumptions and related information used to determine the grant-date fair value of stock options awarded during the six months ended June 30, 2018: | | | | | | | | | | For the Six Months Ended June 30, | | 2018 | | 2017 | Weighted average grant-date fair value per share | $ | 7.82 |
| | $ | 7.15 |
| Expected term (in years) | 6 |
| | 6 |
| Expected stock volatility | 41.1 | % | | 38.1 | % | Dividend yield | — | % | | — | % | Risk-free interest rate | 2.5 | % | | 2.0 | % |
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| Summary of Stock Option Activity |
The following table provides information about stock option awards outstanding during the six months ended June 30, 2018: | | | | | | | | | | | | | | | Options | | Weighted Average Exercise Price | | Weighted Average Remaining Term (in years) | | Aggregate Intrinsic Value (in thousands) | Outstanding as of December 31, 2017 | 4,290,001 |
| | $ | 16.15 |
| | | | | Granted | 226,500 |
| | 18.10 |
| | | | | Exercised | (38,332 | ) | | 15.05 |
| | | | | Forfeited | (106,002 | ) | | 15.86 |
| | | | | Outstanding as of June 30, 2018 | 4,372,167 |
| | 16.27 |
| | 8.6 | | $ | 8,200 |
| Exercisable as of June 30, 2018 | 1,122,775 |
| | 15.81 |
| | 8.4 | | 2,522 |
| Unvested Options at June 30, 2018 | 3,160,171 |
| | 16.36 |
| | 8.6 | | 5,677 |
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