Investments in Unconsolidated Affiliates (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Jun. 30, 2015
Schedule of Equity Method Investments [Line Items]
Investments in unconsolidated affiliates		$ 2,628.5	$ 3,042.0
Equity in income (loss) of unconsolidated affiliates by business segment [Abstract]
Equity in income (loss) of unconsolidated affiliates		373.6	259.5	$ 167.3
Unamortized excess cost amounts by business segment [Abstract]
Unamortized excess cost amounts		46.9	59.6
Equity method investment amortization of excess cost		4.9	3.3	3.3
Forecasted amortization of excess cost amounts - 2016		2.2
Forecasted amortization of excess cost amounts - 2017		2.2
Forecasted amortization of excess cost amounts - 2018		2.2
Forecasted amortization of excess cost amounts - 2019		2.2
Forecasted amortization of excess cost amounts - 2020		2.2
Equity Method Investment, Summarized Financial Information, Balance Sheet [Abstract]
Current assets		204.5	289.9
Property, plant and equipment, net		5,671.1	6,766.5
Other assets		58.9	60.4
Total assets		5,934.5	7,116.8
Current liabilities		306.7	305.9
Other liabilities		103.2	309.9
Combined equity		5,524.6	6,501.0
Total liabilities and combined equity		5,934.5	7,116.8
Equity Method Investment, Summarized Financial Information, Income Statement [Abstract]
Revenues		1,426.6	1,311.3	947.4
Operating income		825.8	600.0	423.9
Net income		814.1	587.9	382.6
NGL Pipelines & Services [Member]
Equity in income (loss) of unconsolidated affiliates by business segment [Abstract]
Equity in income (loss) of unconsolidated affiliates		57.5	30.6	15.7
Unamortized excess cost amounts by business segment [Abstract]
Unamortized excess cost amounts		$ 25.3	26.5
NGL Pipelines & Services [Member] | Venice Energy Service Company, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Interest (in hundredths)		13.10%
Investments in unconsolidated affiliates		$ 25.9	27.7
NGL Pipelines & Services [Member] | K/D/S Promix, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Interest (in hundredths)		50.00%
Investments in unconsolidated affiliates		$ 38.3	38.5
NGL Pipelines & Services [Member] | Baton Rouge Fractionators LLC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Interest (in hundredths)		32.20%
Investments in unconsolidated affiliates		$ 18.5	18.8
NGL Pipelines & Services [Member] | Skelly-Belvieu Pipeline Company, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Interest (in hundredths)		50.00%
Investments in unconsolidated affiliates		$ 39.8	40.1
NGL Pipelines & Services [Member] | Texas Express Pipeline LLC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Interest (in hundredths)		35.00%
Investments in unconsolidated affiliates		$ 342.0	349.3
NGL Pipelines & Services [Member] | Texas Express Gathering LLC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Interest (in hundredths)		45.00%
Investments in unconsolidated affiliates		$ 36.8	37.9
NGL Pipelines & Services [Member] | Front Range Pipeline LLC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Interest (in hundredths)		33.30%
Investments in unconsolidated affiliates		$ 171.2	170.0
NGL Pipelines & Services [Member] | Delaware Basin Gas Processing LLC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Interest (in hundredths)		50.00%
Investments in unconsolidated affiliates		$ 46.2	0.0
Crude Oil Pipelines & Services [Member]
Equity in income (loss) of unconsolidated affiliates by business segment [Abstract]
Equity in income (loss) of unconsolidated affiliates		281.4	184.6	140.3
Unamortized excess cost amounts by business segment [Abstract]
Unamortized excess cost amounts		$ 19.3	21.7
Crude Oil Pipelines & Services [Member] | Seaway Crude Pipeline Company LLC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Interest (in hundredths)		50.00%
Investments in unconsolidated affiliates		$ 1,396.0	1,431.2
Crude Oil Pipelines & Services [Member] | Eagle Ford Pipeline LLC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Interest (in hundredths)		50.00%
Investments in unconsolidated affiliates		$ 388.8	336.5
Crude Oil Pipelines & Services [Member] | Eagle Ford Terminals Corpus Christi LLC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Interest (in hundredths)		50.00%
Investments in unconsolidated affiliates		$ 28.6	0.0
Natural Gas Pipelines & Services [Member]
Equity in income (loss) of unconsolidated affiliates by business segment [Abstract]
Equity in income (loss) of unconsolidated affiliates		$ 3.8	3.6	3.8
Natural Gas Pipelines & Services [Member] | White River Hub, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Interest (in hundredths)		50.00%
Investments in unconsolidated affiliates		$ 22.5	23.2
Petrochemical & Refined Products Services [Member]
Equity in income (loss) of unconsolidated affiliates by business segment [Abstract]
Equity in income (loss) of unconsolidated affiliates	[1]	(15.7)	(13.3)	(22.3)
Unamortized excess cost amounts by business segment [Abstract]
Unamortized excess cost amounts		$ 2.3	2.4
Petrochemical & Refined Products Services [Member] | Baton Rouge Propylene Concentrator, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Interest (in hundredths)		30.00%
Investments in unconsolidated affiliates		$ 5.4	6.5
Petrochemical & Refined Products Services [Member] | Centennial Pipeline LLC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Interest (in hundredths)		50.00%
Investments in unconsolidated affiliates		$ 65.6	66.1
Petrochemical & Refined Products Services [Member] | Other Unconsolidated Affiliates [Member]
Schedule of Equity Method Investments [Line Items]
Investments in unconsolidated affiliates		2.9	2.5
Offshore Pipelines & Services [Member]
Schedule of Equity Method Investments [Line Items]
Investments in unconsolidated affiliates		0.0	493.7		$ 482.4
Equity in income (loss) of unconsolidated affiliates by business segment [Abstract]
Equity in income (loss) of unconsolidated affiliates		46.6	54.0	$ 29.8
Unamortized excess cost amounts by business segment [Abstract]
Unamortized excess cost amounts	[2]	$ 0.0	$ 9.0

[1] Losses are primarily attributable to our investment in Centennial. As a result of a trend in declining earnings, we estimated the fair value of this equity-method investment during each of the last three fiscal years. Our estimates, based on a combination of the market and income approaches, indicate that the fair value of this investment remains substantially in excess of its carrying value.

[2] Our investments in unconsolidated affiliates classified within the Offshore Pipelines & Services segment were sold to Genesis in July 2015.