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Revenue (Details)
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Product revenue      
Disaggregation of revenues      
Total revenue 57.00% 53.00% 55.00%
Rental revenue      
Disaggregation of revenues      
Total revenue 22.00% 25.00% 23.00%
Field service and other revenue      
Disaggregation of revenues      
Total revenue 21.00% 22.00% 22.00%