Subsequent Events (Details) - USD ($)
$ in Thousands
3 Months Ended
Aug. 03, 2018
Jul. 09, 2018
Jul. 06, 2018
Mar. 19, 2018
Feb. 21, 2018
Jun. 30, 2018
Dec. 31, 2017
Subsequent event | CEMP              
Subsequent Events              
Base and earn-out payments made   $ 4,400          
Term Loans              
Subsequent Events              
Repayments of debt       $ 27,000 $ 10,000 $ 23,000  
Principal outstanding           $ 300,000 $ 499,750
Term Loans | Subsequent event              
Subsequent Events              
Repayments of debt $ 5,000   $ 15,000        
Principal outstanding $ 280,000