Business Segment Information - Total Assets By Reportable Segment (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Segment Reporting Information [Line Items]
Total assets	$ 2,498,278	$ 2,596,731
Reportable Segments | Well Intervention
Segment Reporting Information [Line Items]
Total assets	2,134,081	2,180,180
Reportable Segments | Robotics
Segment Reporting Information [Line Items]
Total assets	132,550	151,478
Reportable Segments | Production Facilities
Segment Reporting Information [Line Items]
Total assets	129,773	142,624
Corporate and Other
Segment Reporting Information [Line Items]
Total assets	$ 101,874	$ 122,449