| Stock-based Compensation - Valuation Assumptions (Details) | 12 Months Ended | |
|---|---|---|
| Dec. 31, 2017 | Dec. 31, 2016 | |
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||
| Expected life (in years) | 6 years 6 months | 6 years 6 months | 
| Volatility | 37.00% | 37.00% | 
| Dividend yield | 0.00% | 0.00% | 
| Minimum | ||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||
| Risk-free interest rate | 1.86% | 1.86% | 
| Maximum | ||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||
| Risk-free interest rate | 2.00% | 2.00% | 
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- Definition The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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- Definition The risk-free interest rate assumption that is used in valuing an option on its own shares. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. No definition available. 
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- Definition The estimated measure of the percentage amount by which a share price is expected to fluctuate during the expected term of a nonvested share or option award issued to other than an employee. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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- Definition Expected term of share-based compensation awards, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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