Annual report pursuant to Section 13 and 15(d)

Summary of Significant Accounting Policies - Additional Information (Details)

v3.19.3.a.u2
Summary of Significant Accounting Policies - Additional Information (Details)
$ in Thousands
3 Months Ended 9 Months Ended 12 Months Ended
Dec. 31, 2019
USD ($)
country
Sep. 30, 2019
USD ($)
Jun. 30, 2019
USD ($)
Mar. 31, 2019
USD ($)
Dec. 31, 2018
USD ($)
Sep. 30, 2018
USD ($)
Jun. 30, 2018
USD ($)
Mar. 31, 2018
USD ($)
Dec. 31, 2019
USD ($)
country
Dec. 31, 2019
country
Dec. 31, 2018
USD ($)
Concentration Risk [Line Items]                      
Number of countries entity has operated in since inception (more than) | country 60               60 60  
Percentage accounted for under the equity method 50.00%               50.00% 50.00%  
Cash collateral paid in support of letters of credit outstanding                     $ 9,800
Compensating balances         $ 600           600
Reimbursable revenues $ 156,281 $ 160,083 $ 156,031 $ 157,397 $ 129,148 $ 123,395 $ 118,603 $ 109,675 $ 472,395   $ 480,821
Minimum                      
Concentration Risk [Line Items]                      
Intangible assets, weighted average amortization period                   3 years  
Maximum                      
Concentration Risk [Line Items]                      
Intangible assets, weighted average amortization period                   6 years  
Customer Concentration Risk | Sales Revenue, Net | Exxon Neftegas Limited (ENL)                      
Concentration Risk [Line Items]                      
Percentage of revenue from major customer       31.20%         29.30%   25.70%
Customer Concentration Risk | Sales Revenue, Net of Reimbursable Revenues | Exxon Neftegas Limited (ENL)                      
Concentration Risk [Line Items]                      
Percentage of revenue from major customer                 18.60%   17.90%
Reimbursable revenue                      
Concentration Risk [Line Items]                      
Reimbursable revenues       $ 28,541         $ 70,174   $ 54,620
Reimbursable revenue | Exxon Neftegas Limited (ENL)                      
Concentration Risk [Line Items]                      
Reimbursable revenues       $ 26,300         $ 63,200   $ 47,200
Reimbursable revenue | Customer Concentration Risk | Sales Revenue, Net | Exxon Neftegas Limited (ENL)                      
Concentration Risk [Line Items]                      
Percentage of revenue from major customer       17.70%