Stock-Based Compensation (Tables)
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12 Months Ended |
Dec. 31, 2015 |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Schedule of Allocated Share-based Compensation Expense |
The Company recognized the following stock-based compensation expense in direct operating expense and sales, general and administrative expense in the consolidated statements of operations: | | | | | | | | | | | | | | Years ended December 31, | (Dollars in millions) | 2015 | | 2014 | | 2013 | Stock options | $ | 1.9 |
| | $ | 1.7 |
| | $ | 1.5 |
| Stock appreciation rights | 0.4 |
| | — |
| | — |
| Restricted stock units | 9.0 |
| | 5.8 |
| | 3.2 |
| Performance-based restricted stock units | 17.0 |
| | — |
| | — |
| Warrants | 8.5 |
| | — |
| | — |
| Stock-based compensation expense | $ | 36.8 |
| | $ | 7.5 |
| | $ | 4.7 |
|
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| Stock options |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Schedule of Valuation Assumptions |
The following is a summary of the weighted-average assumptions used to calculate the grant-date fair value using the Black-Scholes option pricing model: | | | | | | | | | |
| 2015 | | 2014 | | 2013 | Weighted-average risk-free interest rate | 1.6 | % | | 1.9 | % | | 1.6 | % | Weighted-average volatility | 60.7 | % | | 50.5 | % | | 51.0 | % | Weighted-average dividend yield | — |
| | — |
| | — |
| Weighted-average expected option term (in years) | 6.61 |
| | 6.44 |
| | 6.44 |
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| Equity Awards Outstanding and Exercisable |
A summary of stock option award activity for the years ended December 31, 2015, 2014 and 2013 is presented below: | | | | | | | | | | | | | | | | | Stock Options | | Number of Stock Options | | Weighted-Average Exercise Price | | Exercise Price Range | | Weighted-Average Grant Date Fair Value | | Weighted-Average Remaining Term | | | | | | | | | | | Outstanding at December 31, 2012 | 1,383,332 |
| | $ | 10.06 |
| | $2.28 - $18.07 | | $ | 5.50 |
| | 8.29 | Granted | 111,000 |
| | 20.18 |
| | $16.57 - $23.19 | | 10.13 |
| | | Exercised | (57,464 | ) | | 4.59 |
| | $2.96 - $6.08 | | 11.62 |
| | | Forfeited | (15,348 | ) | | 14.25 |
| | $6.08 - $16.57 | | 6.99 |
| | | Outstanding at December 31, 2013 | 1,421,520 |
| | $ | 11.02 |
| | $2.28 - $23.19 | | $ | 6.01 |
| | 6.93 | Granted | 50,000 |
| | 27.48 |
| | $23.31 - $31.28 | | 14.37 |
| | | Exercised | (74,531 | ) | | 6.83 |
| | $2.96 - $17.10 | | 18.43 |
| | | Forfeited | (52,194 | ) | | 15.21 |
| | $10.53 - $31.28 | | 7.50 |
| | | Outstanding at December 31, 2014 | 1,344,795 |
| | $ | 11.70 |
| | $2.68 - $27.87 | | $ | 6.04 |
| | 6.84 | Granted | 85,755 |
| | 26.72 |
| | $26.63 - $27.47 | | 15.71 |
| | | Assumed | 883,733 |
| | 24.17 |
| | $10.94 - $31.88 | | 5.71 |
| | | Exercised | (271,703 | ) | | 19.20 |
| | $2.68 - $29.79 | | 4.85 |
| | | Forfeited | (38,300 | ) | | 20.51 |
| | $12.10 - $27.87 | | 9.80 |
| | | Outstanding at December 31, 2015 | 2,004,280 |
| | $ | 16.66 |
| | $2.68 - $31.88 | | $ | 6.06 |
| | 4.57 | Options exercisable at December 31, 2015 | 1,680,525 |
| | $ | 16.62 |
| | $2.68 - $31.88 | | $ | 5.49 |
| | 4.05 |
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| Schedule of Estimated Remaining Share Based Compensation Expense |
The remaining estimated compensation expense related to existing stock options is as follows: | | | | | | | | | | | | | | | | | | | | | | Years ended December 31, | (Dollars in millions) | 2016 |
| 2017 |
| 2018 |
| 2019 |
| 2020 | Remaining estimated compensation expense related to existing stock options | $ | 1.2 |
|
| $ | 0.6 |
|
| $ | 0.4 |
|
| $ | 0.1 |
|
| $ | — |
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| Stock appreciation rights |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Equity Awards Outstanding and Exercisable |
The following table summarizes SAR activity for 2015: | | | | | | | | | | | Stock Appreciation Rights | | Number of Rights | | Weighted-Average Exercise Price | | Weighted-Average Remaining Term | | | | | | | Outstanding at December 31, 2014 | — |
| | $ | — |
| | — | Granted | — |
| | — |
| | — | Assumed | 180,789 |
| | 15.61 |
| | — | Exercised | (37,186 | ) | | 15.61 |
| | — | Forfeited | — |
| | — |
| | — | Outstanding at December 31, 2015 | 143,603 |
| | $ | 15.61 |
| | 1.79 | SARs exercisable at December 31, 2015 | 143,603 |
| | $ | 15.61 |
| | 1.79 |
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| Restricted Stock Units and Performance-based Restricted Stock Units |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Schedule of Valuation Assumptions |
The fair value of all grants of RSUs and PRSUs subject to market-based vesting conditions was estimated using the Monte Carlo simulation lattice model and the assumptions noted in the following table. | | | | | | | | | | | 2015 | | 2014 | | 2013 | Weighted-average risk-free interest rate | 1.1 | % | | 1.2 | % | | 1.0 | % | Weighted-average volatility | 41.1 | % | | 44.3 | % | | 50.0 | % | Weighted-average dividend yield | — |
| | — |
| | — |
| Weighted-average term (in years) | 2.98 |
| | 3.59 |
| | 3.78 |
|
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| Equity Awards Outstanding and Exercisable |
A summary of RSU and PRSU award activity for the years ended December 31, 2015, 2014 and 2013 is presented below: | | | | | | | | | | | | | | | | Restricted Stock Units | | Performance-based Restricted Stock Units | | Number of Restricted Stock Units | | Weighted-Average Grant Date Fair Value | | Number of Performance-based Restricted
Stock Units | | Weighted-Average Grant Date Fair Value | | | | | | | | | Outstanding at December 31, 2012 | 883,816 |
| | $ | 11.31 |
| | — |
| | $ | — |
| Granted | 305,714 |
| | 14.38 |
| | 450,000 |
| | 15.15 |
| Vested | (219,875 | ) | | 11.64 |
| | — |
| | — |
| Forfeited | (68,000 | ) | | 10.65 |
| | — |
| | — |
| Outstanding at December 31, 2013 | 901,655 |
| | $ | 13.26 |
| | 450,000 |
| | $ | 13.26 |
| Granted | 175,773 |
| | 29.81 |
| | 1,114,951 |
| | 23.19 |
| Vested | (295,600 | ) | | 14.98 |
| | — |
| | — |
| Forfeited | (89,005 | ) | | 14.94 |
| | (1,000 | ) | | 27.61 |
| Outstanding at December 31, 2014 | 692,823 |
| | $ | 15.23 |
| | 1,563,951 |
| | $ | 20.86 |
| Granted | 329,899 |
| | 25.72 |
| | 537,261 |
| | 24.75 |
| Assumed | 1,088,674 |
| | 26.02 |
| | — |
| | — |
| Vested | (460,895 | ) | | 19.47 |
| | (25,424 | ) | | 31.02 |
| Forfeited | (92,060 | ) | | 27.24 |
| | (88,728 | ) | | 28.15 |
| Outstanding at December 31, 2015 | 1,558,441 |
| | $ | 23.01 |
| | 1,987,060 |
| | $ | 21.47 |
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| Schedule of Estimated Remaining Share Based Compensation Expense |
Remaining estimated compensation expense related to outstanding RSUs and PRSUs is as follows: | | | | | | | | | | | | | | | | | | | | | | Years ended December 31, | (Dollars in millions) | 2016 | | 2017 | | 2018 | | 2019 | | 2020 and thereafter | Remaining estimated compensation expense related to outstanding RSUs and PRSUs deemed probable | $ | 13.1 |
| | $ | 7.2 |
| | $ | 3.1 |
| | $ | 0.6 |
| | $ | 0.9 |
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