Basis of Presentation (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2012	Mar. 31, 2013	Apr. 29, 2013 Boardwalk Pipelines Holding Company [Member]	Apr. 29, 2013 Boardwalk GP, LP [Member]
Basis of Presentation [Line Items]
Number Of Partnerships Common Units Owned By Holding Company			102.7
Number of Partnership's class B units owned by holding company (in units)			22.9
Percent of general partner interest owned by holding company	2.00%	2.00%		2.00%
Percentage of Partnership's equity interests owned by holding company (in hundredths)			55.00%
Prior Period Reclassification Adjustment	$ 0.4

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The number of the Partnership's class B units owned by the holding company.

No definition available.

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The number of the Partnership's common units owned by the holding company.

No definition available.

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The percentage of the Partnership's equity interests owned by the holding company.

No definition available.

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The percent of the general partner interest owned by the holding company.

No definition available.

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The amount of a reclassification adjustment made to prior period financial statement amounts.

No definition available.

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