Property, Plant and Equipment, Significant Sales (Details) $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($)		Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Jun. 30, 2015 USD ($)
Significant Acquisitions and Disposals [Line Items]
Proceeds from disposal of assets	$ 1,608.6		$ 145.3	$ 280.6
Net gains (losses) attributable to disposal of assets	(15.6)		102.1	83.3
Non-cash asset impairment charge	$ 67.0	[1]	$ 3.7	5.6
Offshore Pipelines And Services [Member]
Significant Acquisitions and Disposals [Line Items]
Percentage of segment assets (in hundredths)			0.043
Percentage of gross operating margin (in hundredths)			0.031
Offshore Business [Member]
Significant Acquisitions and Disposals [Line Items]
Description of assets sold	Our Offshore Business served drilling and development regions, including deepwater production fields, in the northern Gulf of Mexico offshore Alabama, Louisiana, Mississippi and Texas and included approximately 2,350 miles of offshore natural gas and crude oil pipelines and six offshore hub platforms.
Proceeds from disposal of assets	$ 1,527.7		$ 0.0	0.0
Net gains (losses) attributable to disposal of assets	(12.3)		$ 0.0	$ 0.0
Non-cash asset impairment charge	54.8
Total loss on sale	$ (67.1)
Sale of Offshore Business:
Net assets of Offshore Business before impairment charge					$ 1,590.0
Current assets					26.9
Property, plant and equipment, net					1,140.0
Investments in unconsolidated affiliates					482.4
Intangible assets, net					37.1
Goodwill					82.0
Total liabilities					116.4
Noncontrolling interests of assets sold					$ 62.2

[1] Includes a $54.8 million charge recorded in connection with the sale of our Offshore Business.