Business Segments, Segment Reporting Information (Details) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015		Dec. 31, 2014
Information by business segment [Abstract]
Gross operating margin										$ 5,674.6	$ 5,230.7	$ 5,332.1
Revenues from third parties										29,196.5	22,965.6	26,955.6
Revenues from related parties										45.0	56.7	72.3
Intersegment and intrasegment revenues										0.0	0.0	0.0
Total revenues		$ 8,426.6	$ 6,886.9	$ 6,607.6	$ 7,320.4	$ 6,478.8	$ 5,920.4	$ 5,617.8	$ 5,005.3	29,241.5	23,022.3	27,027.9
Equity in income (loss) of unconsolidated affiliates										426.0	362.0	373.6
Property, plant and equipment, net		35,620.4				33,292.5				35,620.4	33,292.5	32,034.7
Investments in unconsolidated affiliates		2,659.4				2,677.3				2,659.4	2,677.3	2,628.5
Intangible assets, net		3,690.3				3,864.1				3,690.3	3,864.1	4,037.2
Goodwill		5,745.2				5,745.2				5,745.2	5,745.2	5,745.2		$ 4,300.2
Segment assets		47,715.3				45,579.1				47,715.3	45,579.1	44,445.6
NGL Pipelines and Services [Member]
Information by business segment [Abstract]
Total revenues										12,468.0	10,242.5	9,788.0
Equity in income (loss) of unconsolidated affiliates										73.4	61.4	57.5
Intangible assets, net		322.3				350.2				322.3	350.2
Goodwill		2,651.7				2,651.7				2,651.7	2,651.7	2,651.7		2,210.2
Crude Oil Pipelines & Services [Member]
Information by business segment [Abstract]
Total revenues										8,156.8	6,515.0	10,305.9
Equity in income (loss) of unconsolidated affiliates										358.4	311.9	281.4
Intangible assets, net		2,186.5				2,279.0				2,186.5	2,279.0
Goodwill		1,841.0				1,841.0				1,841.0	1,841.0	1,841.0		918.7
Natural Gas Pipelines & Services [Member]
Information by business segment [Abstract]
Total revenues										3,145.6	2,543.0	2,743.3
Equity in income (loss) of unconsolidated affiliates										3.8	3.8	3.8
Intangible assets, net		1,018.4				1,054.5				1,018.4	1,054.5
Goodwill		296.3				296.3				296.3	296.3	296.3		296.3
Petrochemical & Refined Products Services [Member]
Information by business segment [Abstract]
Total revenues										5,471.1	3,721.8	4,111.9
Equity in income (loss) of unconsolidated affiliates	[1]									(9.6)	(15.1)	(15.7)
Intangible assets, net		163.1				180.4				163.1	180.4
Goodwill		956.2				956.2				956.2	956.2	956.2		793.0
Offshore Pipelines And Services [Member]
Information by business segment [Abstract]
Total revenues										0.0	0.0	78.8
Equity in income (loss) of unconsolidated affiliates										0.0	0.0	46.6	[2]
Goodwill		0.0				0.0				0.0	0.0	0.0		$ 82.0
Reportable Business Segments [Member] | NGL Pipelines and Services [Member]
Information by business segment [Abstract]
Gross operating margin										3,258.3	2,990.6	2,771.6
Revenues from third parties										12,455.7	10,232.7	9,779.0
Revenues from related parties										12.3	9.8	9.0
Intersegment and intrasegment revenues										27,278.6	19,150.0	10,217.9
Total revenues										39,746.6	29,392.5	20,005.9
Equity in income (loss) of unconsolidated affiliates										73.4	61.4	57.5
Property, plant and equipment, net		13,831.2				14,091.5				13,831.2	14,091.5	12,909.7
Investments in unconsolidated affiliates		733.9				750.4				733.9	750.4	718.7
Intangible assets, net		322.3				350.2				322.3	350.2	380.3
Goodwill		2,651.7				2,651.7				2,651.7	2,651.7	2,651.7
Segment assets		17,539.1				17,843.8				17,539.1	17,843.8	16,660.4
Reportable Business Segments [Member] | Crude Oil Pipelines & Services [Member]
Information by business segment [Abstract]
Gross operating margin										987.2	854.6	961.9
Revenues from third parties										8,137.2	6,478.7	10,258.3
Revenues from related parties										19.6	36.3	47.6
Intersegment and intrasegment revenues										15,943.0	9,052.0	5,162.0
Total revenues										24,099.8	15,567.0	15,467.9
Equity in income (loss) of unconsolidated affiliates										358.4	311.9	281.4
Property, plant and equipment, net		5,208.4				4,216.1				5,208.4	4,216.1	3,550.3
Investments in unconsolidated affiliates		1,839.2				1,824.6				1,839.2	1,824.6	1,813.4
Intangible assets, net		2,186.5				2,279.0				2,186.5	2,279.0	2,377.5
Goodwill		1,841.0				1,841.0				1,841.0	1,841.0	1,841.0
Segment assets		11,075.1				10,160.7				11,075.1	10,160.7	9,582.2
Reportable Business Segments [Member] | Natural Gas Pipelines & Services [Member]
Information by business segment [Abstract]
Gross operating margin										714.5	734.9	782.6
Revenues from third parties										3,132.5	2,532.4	2,729.5
Revenues from related parties										13.1	10.6	13.8
Intersegment and intrasegment revenues										850.8	668.5	662.1
Total revenues										3,996.4	3,211.5	3,405.4
Equity in income (loss) of unconsolidated affiliates										3.8	3.8	3.8
Property, plant and equipment, net		8,375.0				8,403.0				8,375.0	8,403.0	8,620.0
Investments in unconsolidated affiliates		20.8				21.7				20.8	21.7	22.5
Intangible assets, net		1,018.4				1,054.5				1,018.4	1,054.5	1,087.7
Goodwill		296.3				296.3				296.3	296.3	296.3
Segment assets		9,710.5				9,775.5				9,710.5	9,775.5	10,026.5
Reportable Business Segments [Member] | Petrochemical & Refined Products Services [Member]
Information by business segment [Abstract]
Gross operating margin										714.6	650.6	718.5
Revenues from third parties										5,471.1	3,721.8	4,111.9
Revenues from related parties										0.0	0.0	0.0
Intersegment and intrasegment revenues										1,766.9	1,234.8	1,126.0
Total revenues										7,238.0	4,956.6	5,237.9
Equity in income (loss) of unconsolidated affiliates										(9.6)	(15.1)	(15.7)
Property, plant and equipment, net		3,507.7				3,261.2				3,507.7	3,261.2	3,060.7
Investments in unconsolidated affiliates		65.5				80.6				65.5	80.6	73.9
Intangible assets, net		163.1				180.4				163.1	180.4	191.7
Goodwill		956.2				956.2				956.2	956.2	956.2
Segment assets		4,692.5				4,478.4				4,692.5	4,478.4	4,282.5
Reportable Business Segments [Member] | Offshore Pipelines And Services [Member]
Information by business segment [Abstract]
Gross operating margin										0.0	0.0	97.5
Revenues from third parties										0.0	0.0	76.9
Revenues from related parties										0.0	0.0	1.9
Intersegment and intrasegment revenues										0.0	0.0	0.6
Total revenues										0.0	0.0	79.4
Equity in income (loss) of unconsolidated affiliates										0.0	0.0	46.6
Property, plant and equipment, net		0.0				0.0				0.0	0.0	0.0
Investments in unconsolidated affiliates		0.0				0.0				0.0	0.0	0.0
Intangible assets, net		0.0				0.0				0.0	0.0	0.0
Goodwill		0.0				0.0				0.0	0.0	0.0
Segment assets		0.0				0.0				0.0	0.0	0.0
Adjustments [Member]
Information by business segment [Abstract]
Revenues from third parties										0.0	0.0	0.0
Revenues from related parties										0.0	0.0	0.0
Intersegment and intrasegment revenues										(45,839.3)	(30,105.3)	(17,168.6)
Total revenues										(45,839.3)	(30,105.3)	(17,168.6)
Equity in income (loss) of unconsolidated affiliates										0.0	0.0	0.0
Property, plant and equipment, net		4,698.1				3,320.7				4,698.1	3,320.7	3,894.0
Investments in unconsolidated affiliates		0.0				0.0				0.0	0.0	0.0
Intangible assets, net		0.0				0.0				0.0	0.0	0.0
Goodwill		0.0				0.0				0.0	0.0	0.0
Segment assets		$ 4,698.1				$ 3,320.7				$ 4,698.1	$ 3,320.7	$ 3,894.0

[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 market and income approaches, indicate that the fair value of this investment remains in excess of its carrying value.

[2] Our investments in unconsolidated affiliates classified within the Offshore Pipelines & Services segment were sold in July 2015 (see Note 10).