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Equity-Based Compensation (Tables) | 12 Months Ended
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Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract] |
Summary of Restricted Stock and RSU to be Settled in Common Stock Activity | A summary of the activity for RSUs to be settled in common stock for the year ended December 31, 2017 is as follows (shares in thousands):
| Shares |  | Weighted Average Grant Date Fair Value (Per share)
Unvested at December 31, 2016 | 2,711 |  |  | $25.45
Granted | 1,459 |  |  | $37.06
Vested | (1,489 | ) |  | $28.03
Forfeited | (81 | ) |  | $27.58
Unvested at December 31, 2017 | 2,600 |  |  | $30.42
Grant Date Fair Value for Awards of Performance Units Inputs | The grant date fair value for awards of performance units with market-based metrics, which were granted in the year ended December 31, 2017, was based on a fair value as determined using a Monte Carlo simulation valuation methodology using the following key inputs:
Valuation date stock price based on the March 22, 2017 closing stock price | $36.31
Expected volatility | 36.00 | %
Risk-free interest rate | 1.46 | %
Term in years | 2.78 |

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- Definition Schedule Of Share Based Payment Award, Equity Instruments Other Than Options, Valuation Assumptions [Table Text Block] + References No definition available. + Details
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- Definition Tabular disclosure of the changes in outstanding nonvested shares. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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