Quarterly report pursuant to Section 13 or 15(d)

Segment Disclosures - Narrative (Details)

v3.10.0.1
Segment Disclosures - Narrative (Details)
6 Months Ended 12 Months Ended
Jun. 30, 2018
jacket
segment
Dec. 31, 2017
segment
Segment Reporting [Abstract]    
Number of operating segments 4  
Number of corporate non-operating segments   1
Number of jackets and piles constructed | jacket 5