Intangible Assets and Goodwill, Intangible Assets (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Identifiable intangible assets [Abstract]
Gross Value	$ 5,255.1	$ 5,267.2
Accumulated Amortization	(1,564.8)	(1,403.1)
Carrying Value	3,690.3	3,864.1	$ 4,037.2
Amortization expense	166.9	171.3	174.1
Forecasted amortization expense [Abstract]
2018	174.5
2019	165.8
2020	150.7
2021	145.6
2022	141.6
Customer relationship intangibles [Member]
Identifiable intangible assets [Abstract]
Carrying Value	3,410.0
Contract-based intangibles [Member]
Identifiable intangible assets [Abstract]
Carrying Value	285.2
NGL Pipelines & Services [Member]
Identifiable intangible assets [Abstract]
Gross Value	728.2	727.3
Accumulated Amortization	(405.9)	(377.1)
Carrying Value	322.3	350.2
Amortization expense	28.9	30.6	33.6
NGL Pipelines & Services [Member] \| Customer relationship intangibles [Member]
Identifiable intangible assets [Abstract]
Gross Value	447.4	447.4
Accumulated Amortization	(187.5)	(172.7)
Carrying Value	259.9	274.7
NGL Pipelines & Services [Member] \| Contract-based intangibles [Member]
Identifiable intangible assets [Abstract]
Gross Value	280.8	279.9
Accumulated Amortization	(218.4)	(204.4)
Carrying Value	62.4	75.5
Crude Oil Pipelines & Services [Member]
Identifiable intangible assets [Abstract]
Gross Value	2,484.5	2,485.4
Accumulated Amortization	(298.0)	(206.4)
Carrying Value	2,186.5	2,279.0
Amortization expense	92.5	98.4	87.1
Crude Oil Pipelines & Services [Member] \| Customer relationship intangibles [Member]
Identifiable intangible assets [Abstract]
Gross Value	2,203.5	2,204.4
Accumulated Amortization	(127.0)	(84.5)
Carrying Value	2,076.5	2,119.9
Crude Oil Pipelines & Services [Member] \| Contract-based intangibles [Member]
Identifiable intangible assets [Abstract]
Gross Value	281.0	281.0
Accumulated Amortization	(171.0)	(121.9)
Carrying Value	110.0	159.1
Natural Gas Pipelines & Services [Member]
Identifiable intangible assets [Abstract]
Gross Value	1,815.0	1,815.0
Accumulated Amortization	(796.6)	(760.5)
Carrying Value	1,018.4	1,054.5
Amortization expense	36.2	33.2	40.0
Natural Gas Pipelines & Services [Member] \| Customer relationship intangibles [Member]
Identifiable intangible assets [Abstract]
Gross Value	1,350.3	1,350.3
Accumulated Amortization	(417.1)	(390.0)
Carrying Value	933.2	960.3
Natural Gas Pipelines & Services [Member] \| Contract-based intangibles [Member]
Identifiable intangible assets [Abstract]
Gross Value	464.7	464.7
Accumulated Amortization	(379.5)	(370.5)
Carrying Value	85.2	94.2
Petrochemical & Refined Products Services [Member]
Identifiable intangible assets [Abstract]
Gross Value	227.4	239.5
Accumulated Amortization	(64.3)	(59.1)
Carrying Value	163.1	180.4
Amortization expense	9.3	9.1	8.9
Petrochemical & Refined Products Services [Member] \| Customer relationship intangibles [Member]
Identifiable intangible assets [Abstract]
Gross Value	181.4	185.5
Accumulated Amortization	(45.9)	(43.9)
Carrying Value	135.5	141.6
Petrochemical & Refined Products Services [Member] \| Contract-based intangibles [Member]
Identifiable intangible assets [Abstract]
Gross Value	46.0	54.0
Accumulated Amortization	(18.4)	(15.2)
Carrying Value	27.6	38.8
Offshore Pipelines & Services [Member]
Identifiable intangible assets [Abstract]
Amortization expense	$ 0.0	$ 0.0	$ 4.5

The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6388964&loc=d3e16225-109274

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275

+ Details

Name:	us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized during the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References