Business Segment Information - Total Assets By Reportable Segment (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Total assets	$ 2,361,562	$ 2,246,941
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Total assets	321,559	305,331
Well Intervention [Member] | Reportable Segments [Member]
Segment Reporting Information [Line Items]
Total assets	1,719,971	1,596,517
Robotics [Member] | Reportable Segments [Member]
Segment Reporting Information [Line Items]
Total assets	168,734	186,901
Production Facilities [Member] | Reportable Segments [Member]
Segment Reporting Information [Line Items]
Total assets	$ 151,298	$ 158,192