Business Segment Information - Total Assets By Reportable Segment (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Total assets	$ 2,339,148	$ 2,362,837
Corporate and Other
Segment Reporting Information [Line Items]
Total assets	214,793	213,959
Well Intervention | Reportable Segments
Segment Reporting Information [Line Items]
Total assets	1,834,166	1,830,733
Robotics | Reportable Segments
Segment Reporting Information [Line Items]
Total assets	155,297	179,853
Production Facilities | Reportable Segments
Segment Reporting Information [Line Items]
Total assets	$ 134,892	$ 138,292