Intangible Assets and Goodwill, Intangible Assets (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Identifiable intangible assets [Abstract]
Gross Value	$ 2,646.6		$ 2,774.0
Accum. Amort.	(990.4)		(932.3)
Carrying Value	1,656.2		1,841.7		1,064.8
Amortization Expense	147.0		137.6		119.9
Forecasted amortization expense [Abstract]
2012	123.3
2013	109.3
2014	106.7
2015	106.2
2016	107.6
Customer relationship intangibles [Member]
Identifiable intangible assets [Abstract]
Carrying Value	1,320.0
Customer relationship intangibles [Member] | State Line Gathering [Member]
Identifiable intangible assets [Abstract]
Gross Value	675.0	[1]
Accum. Amort.	(36.1)	[1]
Carrying Value	638.9	[1]
Customer relationship intangibles [Member] | Fairplay Gathering [Member]
Identifiable intangible assets [Abstract]
Gross Value	116.6	[1]
Accum. Amort.	(11.6)	[1]
Carrying Value	105.0	[1]
Customer relationship intangibles [Member] | Fairplay Processing [Member]
Identifiable intangible assets [Abstract]
Gross Value	103.4	[2]
Accum. Amort.	(10.3)	[2]
Carrying Value	93.1	[2]
Customer relationship intangibles [Member] | State Line and Fairplay [Member]
Identifiable intangible assets [Abstract]
Gross Value	895.0
Accum. Amort.	(58.0)
Carrying Value	837.0
Customer relationship intangibles [Member] | San Juan Gathering [Member]
Identifiable intangible assets [Abstract]
Carrying Value	188.1
Customer relationship intangibles [Member] | Offshore Pipelines and Platforms [Member]
Identifiable intangible assets [Abstract]
Carrying Value	76.6
Customer relationship intangibles [Member] | Encinal [Member]
Identifiable intangible assets [Abstract]
Carrying Value	71.8
Contract-based intangibles [Member]
Identifiable intangible assets [Abstract]
Carrying Value	331.6
Contract-based intangibles [Member] | San Juan Gathering [Member]
Identifiable intangible assets [Abstract]
Carrying Value	69.3
Contract-based intangibles [Member] | Jonah Gas Gathering [Member]
Identifiable intangible assets [Abstract]
Carrying Value	104.0
Contract-based intangibles [Member] | Shell Processing Agreement [Member]
Identifiable intangible assets [Abstract]
Carrying Value	83.8
NGL Pipelines & Services [Member]
Identifiable intangible assets [Abstract]
Gross Value	639.2		663.0
Accum. Amort.	(297.9)		(283.3)
Carrying Value	341.3		379.7		315.6
Amortization Expense	41.1		40.1		36.9
NGL Pipelines & Services [Member] | Customer relationship intangibles [Member]
Identifiable intangible assets [Abstract]
Gross Value	340.8		340.8
Accum. Amort.	(128.2)		(106.7)
Carrying Value	212.6		234.1
NGL Pipelines & Services [Member] | Contract-based intangibles [Member]
Identifiable intangible assets [Abstract]
Gross Value	298.4	[3]	322.2	[3]
Accum. Amort.	(169.7)	[3]	(176.6)	[3]
Carrying Value	128.7	[3]	145.6	[3]
Onshore Natural Gas Pipelines & Services [Member]
Identifiable intangible assets [Abstract]
Gross Value	1,628.4		1,728.9
Accum. Amort.	(500.6)		(482.8)
Carrying Value	1,127.8		1,246.1		527.2
Amortization Expense	77.1		72.7		57.2
Onshore Natural Gas Pipelines & Services [Member] | Customer relationship intangibles [Member]
Identifiable intangible assets [Abstract]
Gross Value	1,163.6		1,163.6
Accum. Amort.	(209.7)		(160.8)
Carrying Value	953.9		1,002.8
Onshore Natural Gas Pipelines & Services [Member] | Contract-based intangibles [Member]
Identifiable intangible assets [Abstract]
Gross Value	464.8	[4]	565.3	[4]
Accum. Amort.	(290.9)	[4]	(322.0)	[4]
Carrying Value	173.9	[4]	243.3	[4]
Onshore Crude Oil Pipelines & Services [Member]
Identifiable intangible assets [Abstract]
Gross Value	10.1		10.1
Accum. Amort.	(4.3)		(3.9)
Carrying Value	5.8		6.2		6.5
Amortization Expense	0.4		0.4		0.4
Onshore Crude Oil Pipelines & Services [Member] | Customer relationship intangibles [Member]
Identifiable intangible assets [Abstract]
Gross Value	9.7		9.7
Accum. Amort.	(4.1)		(3.7)
Carrying Value	5.6		6.0
Onshore Crude Oil Pipelines & Services [Member] | Contract-based intangibles [Member]
Identifiable intangible assets [Abstract]
Gross Value	0.4		0.4
Accum. Amort.	(0.2)		(0.2)
Carrying Value	0.2		0.2
Offshore Pipelines & Services [Member]
Identifiable intangible assets [Abstract]
Gross Value	207.0		207.0
Accum. Amort.	(129.5)		(118.3)
Carrying Value	77.5		88.7		101.5
Amortization Expense	11.2		12.8		14.7
Offshore Pipelines & Services [Member] | Customer relationship intangibles [Member]
Identifiable intangible assets [Abstract]
Gross Value	205.8		205.8
Accum. Amort.	(129.2)		(118.1)
Carrying Value	76.6		87.7
Offshore Pipelines & Services [Member] | Contract-based intangibles [Member]
Identifiable intangible assets [Abstract]
Gross Value	1.2		1.2
Accum. Amort.	(0.3)		(0.2)
Carrying Value	0.9		1.0
Petrochemical & Refined Products Services [Member]
Identifiable intangible assets [Abstract]
Gross Value	161.9		165.0
Accum. Amort.	(58.1)		(44.0)
Carrying Value	103.8		121.0		114.0
Amortization Expense	17.2		11.6		10.7
Petrochemical & Refined Products Services [Member] | Customer relationship intangibles [Member]
Identifiable intangible assets [Abstract]
Gross Value	104.3		104.7
Accum. Amort.	(28.4)		(23.8)
Carrying Value	75.9		80.9
Petrochemical & Refined Products Services [Member] | Contract-based intangibles [Member]
Identifiable intangible assets [Abstract]
Gross Value	57.6		60.3
Accum. Amort.	(29.7)		(20.2)
Carrying Value	$ 27.9		$ 40.1

[1] These natural gas gathering customer relationship intangible assets are a component of our Onshore Natural Gas Pipelines & Services business segment.

[2] The Fairplay natural gas processing customer relationship intangible assets are a component of our NGL Pipelines & Services business segment.

[3] In March 2011, we sold two NGL fractionators that were not strategic to our operations and the related contract-based intangible assets.

[4] In December 2011, we sold our Petal and Hattiesburg, Mississippi underground natural gas storage facilities (i.e., the sale of Crystal) and their related contract-based intangible assets. See Note 8 for additional information regarding the sale of Crystal.