Annual report pursuant to Section 13 and 15(d)

REVENUE - Transaction price allocated to the remaining performance obligations (Details)

v3.19.1
REVENUE - Transaction price allocated to the remaining performance obligations (Details) - Fixed-price contracts
$ in Thousands
 12 Months Ended
Dec. 31, 2018
USD ($)
Transaction price allocated to the remaining performance obligations  
Remaining performance obligation $ 501,604
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01  
Transaction price allocated to the remaining performance obligations  
Remaining performance obligation $ 173,346
Expected timing of satisfaction 1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01  
Transaction price allocated to the remaining performance obligations  
Remaining performance obligation $ 124,425
Expected timing of satisfaction 1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01  
Transaction price allocated to the remaining performance obligations  
Remaining performance obligation $ 203,833
Expected timing of satisfaction