Operations by Business Segment and Geographic Area Operations by Business Segment and Geographic Area - Other Significant Reconciling Items (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting, Asset Reconciling Item [Line Items]
Property, Plant and Equipment, Additions	$ 178,038	$ 104,958	$ 142,513
Oil And Gas [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Property, Plant and Equipment, Additions	173,456	101,331	136,520
ROVs [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Property, Plant and Equipment, Additions	45,732	40,425	50,339
Subsea Products [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Property, Plant and Equipment, Additions	25,149	27,711	56,669
Subsea Projects [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Property, Plant and Equipment, Additions	99,701	29,544	25,602
Asset Integrity [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Property, Plant and Equipment, Additions	2,874	3,651	3,910
Advanced Technologies [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Property, Plant and Equipment, Additions	3,550	2,063	2,742
Corporate and Other [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Property, Plant and Equipment, Additions	$ 1,033	$ 1,564	$ 3,251