Employee Benefit Plans - Additional Information (Details) - USD ($)
$ / shares in Units, $ in Thousands |
12 Months Ended |
Dec. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
Dec. 31, 2014 |
Dec. 31, 2013 |
Dec. 31, 2012 |
Dec. 31, 2011 |
Dec. 31, 2010 |
| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |
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| Company's contributions to employee saving plan |
$ 115
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$ 69
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$ 96
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| Discretionary company's contribition to employee saving plan |
22
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0
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14
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| Compensation expense |
$ 4,296
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$ 3,446
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$ 5,591
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| Share appreciation rights and stock options |
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| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |
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| Method used for the calculation of all stock options awards |
Black-Scholes method
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| Exercised, shares |
0
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0
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0
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143,189
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153,556
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29,251
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130,578
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130,577
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| Expected term simplified method |
4.5 years
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| Fair value of stock granted |
$ 0.78
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$ 0.55
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$ 1.14
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| Vesting Period |
3 years
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| Weighted average time to vest |
2 years
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| Contractual term of the award |
7 years
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| Service Conditions |
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| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |
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| Expected volatility |
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84.71%
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55.17%
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| Risk free rate |
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1.81%
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1.46%
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| Estimated compensation cost relating to non-vested service conditions stock option not yet recognized |
$ 785
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| Estimated compensation cost relating to non-vested service conditions restricted stock and restricted stock units awards not yet recognized |
$ 7,271
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| Years to maturity |
2 years 11 months 4 days
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| Performance Conditions |
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| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |
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| Compensation expense |
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$ 2,615
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| Restricted share unit awards |
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| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |
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| Expected dividend assumption |
$ 0
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$ 0
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$ 0
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| Fair value of stock granted |
1.27
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0.78
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0.55
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| Restricted share unit |
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| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |
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| Expected dividend assumption |
0
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0
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0
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| Fair value of stock granted |
$ 1.27
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$ 1.2
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$ 1.2
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| Tranche - Year 1 | Share appreciation rights and stock options |
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| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |
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| Percentage of vesting of the service conditions options, per each year |
33.30%
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| Tranche - Year 2 | Share appreciation rights and stock options |
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| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |
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| Percentage of vesting of the service conditions options, per each year |
33.30%
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| Tranche - Year 3 | Share appreciation rights and stock options |
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| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |
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| Percentage of vesting of the service conditions options, per each year |
33.40%
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