Fair Value Measurements, Derivatives and Other Comprehensive Income (OCI) Fair Value Measurements Assets and Liabilities Measured on Recurring and Nonrecurring (Details) (USD $) In Millions, unless otherwise specified									3 Months Ended		3 Months Ended			3 Months Ended				3 Months Ended
	Mar. 31, 2013 Fair Value, Measurements, Recurring [Member] Commodity Contract [Member]	Dec. 31, 2012 Fair Value, Measurements, Recurring [Member] Commodity Contract [Member]	Mar. 31, 2013 Fair Value, Measurements, Recurring [Member] Fair Value, Inputs, Level 1 [Member] Commodity Contract [Member]	Dec. 31, 2012 Fair Value, Measurements, Recurring [Member] Fair Value, Inputs, Level 1 [Member] Commodity Contract [Member]	Mar. 31, 2013 Fair Value, Measurements, Recurring [Member] Fair Value, Inputs, Level 2 [Member] Commodity Contract [Member]	Dec. 31, 2012 Fair Value, Measurements, Recurring [Member] Fair Value, Inputs, Level 2 [Member] Commodity Contract [Member]	Mar. 31, 2013 Fair Value, Measurements, Recurring [Member] Fair Value, Inputs, Level 3 [Member] Commodity Contract [Member]	Dec. 31, 2012 Fair Value, Measurements, Recurring [Member] Fair Value, Inputs, Level 3 [Member] Commodity Contract [Member]	Mar. 31, 2012 Fair Value, Measurements, Nonrecurring [Member]	Dec. 31, 2012 Fair Value, Measurements, Nonrecurring [Member]	Mar. 31, 2012 Fair Value, Measurements, Nonrecurring [Member] Assets to be abandoned [Member]		Dec. 31, 2012 Fair Value, Measurements, Nonrecurring [Member] Assets to be abandoned [Member]	Sep. 30, 2012 Fair Value, Measurements, Nonrecurring [Member] Assets Held-for-sale [Member]	Mar. 31, 2012 Fair Value, Measurements, Nonrecurring [Member] Assets Held-for-sale [Member]		Dec. 31, 2012 Fair Value, Measurements, Nonrecurring [Member] Assets Held-for-sale [Member]	Mar. 31, 2012 Fair Value, Measurements, Nonrecurring [Member] Asset retirement obligation associated with retirement of small-diameter pipe [Member]		Dec. 31, 2012 Fair Value, Measurements, Nonrecurring [Member] Asset retirement obligation associated with retirement of small-diameter pipe [Member]	Dec. 31, 2012 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 1 [Member]	Dec. 31, 2012 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 1 [Member] Assets to be abandoned [Member]	Dec. 31, 2012 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 1 [Member] Assets Held-for-sale [Member]	Dec. 31, 2012 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 1 [Member] Asset retirement obligation associated with retirement of small-diameter pipe [Member]	Dec. 31, 2012 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 2 [Member]	Dec. 31, 2012 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 2 [Member] Assets to be abandoned [Member]	Dec. 31, 2012 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 2 [Member] Assets Held-for-sale [Member]	Dec. 31, 2012 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 2 [Member] Asset retirement obligation associated with retirement of small-diameter pipe [Member]	Dec. 31, 2012 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 3 [Member]	Dec. 31, 2012 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 3 [Member] Assets to be abandoned [Member]	Dec. 31, 2012 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 3 [Member] Assets Held-for-sale [Member]	Dec. 31, 2012 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 3 [Member] Asset retirement obligation associated with retirement of small-diameter pipe [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure		$ 0.1		$ 0		$ 0.1		$ 0		$ 0			$ 0				$ 0				$ 0	$ 0	$ 0		$ 0	$ 0	$ 0		$ 0	$ 0	$ 0
Liabilities, Fair Value Disclosure	4.9	0.1	0	0	4.9	0.1	0	0												(0.8)				0				0				(0.8)
Asset impairment on small-diameter pipeline assets									1.4
Impairment of Long-Lived Assets to be Disposed of									(3.4)		(0.6)	[1]			(2.8)	[2]
Asset retirement obligations associated with retirement of small-diameter pipeline assets																		(0.8)	[1]
Book Value Before Sale or Impairment														$ 3.0

[1] In 2012, the Partnership determined that it would retire a number of small-diameter pipeline assets and recorded an asset impairment charge of $1.4 million comprised of the carrying amount of the assets and amounts related to asset retirement obligations for the assets

[2] In 2012, the Partnership recognized a $2.8 million impairment charge related to its Owensboro, Kentucky, office building. The office building was sold for an amount that equaled its carrying amount of $3.0 million in the third quarter 2012.