Stock-Based Compensation (Tables)
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12 Months Ended |
Dec. 31, 2019 |
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| Disclosure of Compensation Related Costs, Share-based Payments [Abstract] |
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| Schedule of Compensation Cost for Share-based Payment Arrangements, Allocation of Share-based Compensation Costs by Plan |
The following table summarizes stock-based compensation expense recognized for the periods presented: | | | | | | | | | | | | | | Year Ended December 31, | (in thousands) | 2019 | | 2018 | | 2017 | Restricted stock awards | $ | 15,929 |
| | $ | 9,185 |
| | $ | 5,008 |
| Stock option awards | 9,562 |
| | 9,433 |
| | 8,160 |
| Performance stock units | 3,374 |
| | 2,052 |
| | 591 |
| Other stock-based compensation expense(1) | 132 |
| | — |
| | — |
| Total stock-based compensation expense | $ | 28,997 |
| | $ | 20,670 |
| | $ | 13,759 |
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| Nonvested Restricted Stock Shares Activity |
The following table provides a summary of the restricted stock activity during the year ended December 31, 2019: | | | | | | | | | Awards | | Weighted Average Grant-Date Fair Value | Unvested balance as of December 31, 2018 | 1,535,945 |
| | $ | 17.88 |
| Granted | 4,109,148 |
| | 6.59 |
| Vested | (690,084 | ) | | 17.46 |
| Forfeited | (116,013 | ) | | 11.39 |
| Unvested balance as of December 31, 2019 | 4,838,996 |
| | 8.51 |
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| Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions |
The following table summarizes the assumptions and related information used to determine the grant-date fair value of stock options awarded for the periods presented: | | | | | | | | | | | | | | Years Ended December 31, | | 2019 | | 2018 | | 2017 | Weighted average grant date fair value per share | $ | 4.32 |
| | $ | 8.58 |
| | $ | 7.15 |
| Expected term (in years) | 6 |
| | 6 |
| | 6 |
| Expected stock volatility | 47 | % | | 42 | % | | 38 | % | Dividend yield | — |
| | — |
| | — |
| Risk-free interest rate | 2.2 | % | | 2.7 | % | | 2.0 | % |
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| Schedule of Share-based Compensation, Stock Options, Activity |
The following table provides information about stock option awards outstanding during the year ended December 31, 2019: | | | | | | | | | | | | | | | Options | | Weighted Average Exercise Price | | Weighted Average Remaining Term (in years) | | Aggregate Intrinsic Value (in thousands) | Outstanding as of December 31, 2018 | 4,559,334 |
| | $ | 16.55 |
| | | | | Granted | 346,500 |
| | 9.24 |
| | | | | Exercised | — |
| | — |
| | | | | Forfeited | (103,670 | ) | | 17.76 |
| | | | | Expired | (37,997 | ) | | 17.80 |
| | | | | Outstanding as of December 31, 2019 | 4,764,167 |
| | 15.99 |
| | 7.3 | | $ | 11 |
| Exercisable as of December 31, 2019 | 3,530,630 |
| | 16.00 |
| | 7.0 | | $ | — |
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| Schedule of Share-based Payment Award, Equity Instruments Other Than Options, Valuation Assumptions |
The following table summarizes the key assumptions and related information used to determine the grant-date fair value of performance stock units awarded during the periods presented: | | | | | | | | | | | | | | Year Ended December 31, | | 2019 | | 2018 | | 2017 | Weighted average grant-date fair value per unit | $ | 6.68 |
| | $ | 22.35 |
| | $ | 21.53 |
| Number of simulations | 1,000,000 |
| | 1,000,000 |
| | 1,000,000 |
| Expected stock volatility | 52.3 | % | | 40.2 | % | | 41.6 | % | Dividend yield | — | % | | — | % | | — | % | Risk-free interest rate | 1.8 | % | | 2.8 | % | | 1.5 | % |
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| Share-based Compensation, Performance Shares Award Outstanding Activity |
The following table provides information about performance stock units outstanding during the year ended December 31, 2019: | | | | | | | | | Awards | | Weighted Average Grant Date Fair Value | Unvested balance as of December 31, 2018 | 386,459 |
| | $ | 21.94 |
| Granted | 486,213 |
| | 6.68 |
| Vested | — |
| | — |
| Forfeited | — |
| | — |
| Unvested balance as of December 31, 2019 | 872,672 |
| | 13.44 |
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