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Related-Party Transactions (Details) - Affiliates of Goldman Sachs and Company [Member] - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2018
Mar. 08, 2018
Related Party Transaction [Line Items]    
Revenue from Related Parties $ 10.5  
one director [Member]    
Related Party Transaction [Line Items]    
Ownership Percentage   10.00%