Related Party Transactions (Narrative) (Details) - Equity Method Investee - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Related Party Transaction [Line Items]
Trade receivables	$ 100.0		$ 100.0		$ 98.4
Trade payables	16.7		16.7		121.8
Note receivables	129.5		129.5		140.9
Revenue	60.2	$ 33.0	152.7	$ 68.4
Expenses	2.6	22.3	6.0	62.9
TP JGC Coral France SNC
Related Party Transaction [Line Items]
Trade receivables	66.5		66.5		42.5
Revenue	33.2		61.4
Technip Odebrecht PLSV CV
Related Party Transaction [Line Items]
Trade receivables	10.6		10.6		13.8
Revenue		4.3		6.5
Anadarko
Related Party Transaction [Line Items]
Trade receivables					22.3
Revenue	25.2	20.6	75.5	37.3
Dofcon Brasil AS
Related Party Transaction [Line Items]
Trade payables	12.1		12.1
Note receivables	$ 117.1		$ 117.1		114.9
JGC Corporation
Related Party Transaction [Line Items]
Trade payables					52.4
Expenses		12.3		20.4
Chiyoda
Related Party Transaction [Line Items]
Trade payables					$ 48.3
Expenses		$ 5.2		$ 13.6