Business Segments (Segment Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Total Assets	$ 28,263.7	$ 18,679.3
Operating segments
Segment Reporting Information [Line Items]
Total Assets	19,978.2	11,052.4
Operating segments | Subsea
Segment Reporting Information [Line Items]
Total Assets	12,944.4	7,823.1
Operating segments | Onshore/Offshore
Segment Reporting Information [Line Items]
Total Assets	4,604.8	3,229.3
Operating segments | Surface Technologies
Segment Reporting Information [Line Items]
Total Assets	2,453.3
Intercompany eliminations
Segment Reporting Information [Line Items]
Total Assets	(24.3)
Corporate
Segment Reporting Information [Line Items]
Total Assets	$ 8,285.5	$ 7,626.9