Business Segment Information - Total Assets By Reportable Segment (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Total assets	$ 2,366,844	$ 2,362,837
Corporate and Other
Segment Reporting Information [Line Items]
Total assets	201,131	213,959
Well Intervention | Reportable Segments
Segment Reporting Information [Line Items]
Total assets	1,885,738	1,830,733
Robotics | Reportable Segments
Segment Reporting Information [Line Items]
Total assets	152,876	179,853
Production Facilities | Reportable Segments
Segment Reporting Information [Line Items]
Total assets	$ 127,099	$ 138,292