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	6 Months Ended										3 Months Ended	6 Months Ended		3 Months Ended		6 Months Ended			3 Months Ended			6 Months Ended			3 Months Ended	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2012	Jun. 30, 2012 Owensboro Office Building [Member]	Jun. 30, 2013 Fair Value, Measurements, Recurring [Member] Commodity Contract [Member]	Dec. 31, 2012 Fair Value, Measurements, Recurring [Member] Commodity Contract [Member]	Jun. 30, 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]	Jun. 30, 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]	Jun. 30, 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]	Jun. 30, 2012 Fair Value, Measurements, Nonrecurring [Member]	Jun. 30, 2012 Fair Value, Measurements, Nonrecurring [Member]	Dec. 31, 2012 Fair Value, Measurements, Nonrecurring [Member]	Jun. 30, 2012 Fair Value, Measurements, Nonrecurring [Member] Assets to be abandoned [Member]		Jun. 30, 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]	Jun. 30, 2012 Fair Value, Measurements, Nonrecurring [Member] Assets Held-for-sale [Member]		Jun. 30, 2012 Fair Value, Measurements, Nonrecurring [Member] Assets Held-for-sale [Member]		Dec. 31, 2012 Fair Value, Measurements, Nonrecurring [Member] Assets Held-for-sale [Member]	Jun. 30, 2012 Fair Value, Measurements, Nonrecurring [Member] Asset retirement obligation associated with retirement of small-diameter pipe [Member]	Jun. 30, 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 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 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]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-Lived Assets to be Abandoned, Carrying Value of Asset															$ 2.1		$ 2.1
Assets, Fair Value Disclosure				3.2	0.1	0	0	3.2	0.1	0	0			0					0						0			0	0	0	0	0	0	0	0	0
Liabilities, Fair Value Disclosure				0.9	0.1	0	0	0.9	0.1	0	0
Asset impairment on small-diameter pipeline assets	2.9	4.3
Impairment of Long-Lived Assets to be Disposed of			(2.8)									(1.5)	(4.9)		(1.5)	[1]	(2.1)	[1]			0	[2]	(2.8)	[2]
Asset retirement obligations associated with retirement of small-diameter pipeline assets																										1.4	2.2
Carrying Value Before Sale or Impairment																				$ 3.0

[1] In 2012, the Partnership determined that it would retire a number of small-diameter pipeline assets with a carrying value of $2.1 million. As a result, an asset impairment charge of $2.9 million and $4.3 million was recorded for the three and six months ended June 30, 2012, of which $1.4 million and $2.2 million represent amounts related to the asset retirement obligations recorded in the three and six months ended June 30, 2012 for these 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.