Derivative Instruments, Hedging Activities and Fair Value Measurements, Fair Value Measurements (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Nonfinancial assets and liabilities [Abstract]
Goodwill impairment loss					$ 1.3	[1]
Charge for deficiency fees					28.7
Reconciliation of changes in the fair value of Level 3 financial assets and liabilities [Roll Forward]
Balance, January 1	(25.9)		5.7
Total gains (losses) included in:
Net income	2.3	[2]	25.3	[2]
Other comprehensive income (loss)	16.2		(34.8)
Settlements	(2.0)		(22.6)
Transfers out of Level 3	9.8	[3]	0.5	[3]
Balance, December 31	0.4		(25.9)		5.7
Unrealized gain (loss) recognized as a component of net income related to level 3 financial assets and liabilities	2.6		10.3
Segment Reporting Information [Line Items]
Non-cash asset impairment charges	27.8		8.4		33.5
NGL Pipelines & Services [Member]
Nonfinancial assets and liabilities [Abstract]
Goodwill impairment loss					0	[1]
Segment Reporting Information [Line Items]
Non-cash asset impairment charges	11.3		2.8		4.1
Onshore Natural Gas Pipelines & Services [Member]
Nonfinancial assets and liabilities [Abstract]
Goodwill impairment loss					0	[1]
Segment Reporting Information [Line Items]
Non-cash asset impairment charges	10.4		5.2		4.3
Offshore Pipelines & Services [Member]
Nonfinancial assets and liabilities [Abstract]
Goodwill impairment loss					0	[1]
Segment Reporting Information [Line Items]
Non-cash asset impairment charges	5.5		0		0
Petrochemical & Refined Products Services [Member]
Nonfinancial assets and liabilities [Abstract]
Goodwill impairment loss					1.3	[1]
Segment Reporting Information [Line Items]
Non-cash asset impairment charges	0.6		0.4		25.1
Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Financial assets:
Interest rate derivatives	0		0
Commodity derivatives	28.4		15.7
Foreign currency derivatives			0
Total	28.4		15.7
Financial liabilities:
Interest rate derivatives	0		0
Commodity derivatives	29.9		28.4
Foreign currency derivatives			0
Total	29.9		28.4
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Financial assets:
Interest rate derivatives	87.9		108.1
Commodity derivatives	38.1		49.6
Foreign currency derivatives			0.3
Total	126.0		158.0
Financial liabilities:
Interest rate derivatives	311.4		53.6
Commodity derivatives	34.7		61.9
Foreign currency derivatives			0.1
Total	346.1		115.6
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Financial assets:
Interest rate derivatives	0		0
Commodity derivatives	0.8		25.1
Foreign currency derivatives			0
Total	0.8		25.1
Financial liabilities:
Interest rate derivatives	0		0
Commodity derivatives	0.4		51.0
Foreign currency derivatives			0
Total	0.4		51.0
Fair Value, Measurements, Recurring [Member] | Fair Value [Member]
Financial assets:
Interest rate derivatives	87.9		108.1
Commodity derivatives	67.3		90.4
Foreign currency derivatives			0.3
Total	155.2		198.8
Financial liabilities:
Interest rate derivatives	311.4		53.6
Commodity derivatives	65.0		141.3
Foreign currency derivatives			0.1
Total	376.4		195.0
Fair Value, Measurements, Nonrecurring [Member] | Level 2 [Member]
Nonfinancial assets and liabilities [Abstract]
Spare parts inventory	2.7
Fair Value, Measurements, Nonrecurring [Member] | Level 2 [Member] | Impairment Charges [Member]
Nonfinancial assets and liabilities [Abstract]
Spare parts inventory	11.1
Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member]
Nonfinancial assets and liabilities [Abstract]
Property, plant and equipment	0.4
Property, plant and equipment and other current assets			0.7
Property, plant and equipment, intangible assets, and other current assets					31.4
Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member] | Impairment Charges [Member]
Nonfinancial assets and liabilities [Abstract]
Property, plant and equipment	16.7
Property, plant and equipment and other current assets			8.4
Property, plant and equipment, intangible assets, and other current assets					$ 32.2

[1] See Note 6 for information regarding impairment charges recorded during 2009.

[2] There were unrealized gains of $2.6 million and $10.3 million included in these amounts for the years ended December 31, 2011 and 2010, respectively.

[3] Transfers out of Level 3 into Level 2 during 2011 were primarily due to the change in observability of forward NGL prices as described above.