Business Segment Information - Total Assets By Reportable Segment (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Total assets	$ 2,347,730	$ 2,362,837
Reportable Segments | Well Intervention
Segment Reporting Information [Line Items]
Total assets	1,916,638	1,830,733
Reportable Segments | Robotics
Segment Reporting Information [Line Items]
Total assets	147,602	179,853
Reportable Segments | Production Facilities
Segment Reporting Information [Line Items]
Total assets	120,845	138,292
Corporate and Other
Segment Reporting Information [Line Items]
Total assets	$ 162,645	$ 213,959