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Revenues (Tables)
12 Months Ended
Dec. 31, 2018
Revenue from Contract with Customer [Abstract]  
Schedule of disaggregation of revenues
(in thousands) 2018  2017  2016 
Oil field services transferred at a point in time $-  $-  $- 
Oil field services transferred over time  1,721,005   1,595,227   728,974 
Total revenues $1,721,005  $1,595,227  $728,974 
Schedule of contract assets included in accounts receivable
(in thousands) 2018  2017 
Unbilled trade receivables $56,408  $68,494