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Equity-Based Compensation - Additional Disclosures for Unit Options (Details) - 2005 Common Membership Unit Plan - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Total fair value of unit options vested $ 0 $ 271 $ 835
Total aggregate intrinsic value of unit options exercised $ 869 $ 601 $ 9,098