Financing (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended				6 Months Ended
	Jun. 30, 2013 Total Revolving Credit Facility [Member]	Dec. 31, 2012 Total Revolving Credit Facility [Member]	Jun. 30, 2013 Total Notes and Debentures [Member]	Dec. 31, 2012 Total Notes and Debentures [Member]	Jun. 30, 2012 Gulf South Notes Due 2022 [Member]		Jun. 30, 2013 Term loan Boardwalk Acquisition Company [Member]	Dec. 31, 2012 Term loan Boardwalk Acquisition Company [Member]
Debt Instruments [Abstract]
Long-term Debt, Gross			$ 3,000.0	$ 3,000.0			$ 225.0	$ 225.0
Debt, Weighted Average Interest Rate	1.32%	1.34%	5.32%	5.32%			1.95%	1.96%
Debt Instrument, Issuance Date					Jun. 15, 2012
Debt Instrument, Face Amount					300.0		225.0
Payments of Debt Issuance Costs					3.5
Proceeds from Debt, Net of Issuance Costs					296.5	[1]
Debt Instrument, Interest Rate, Stated Percentage					4.00%
Debt Instrument, Maturity Date					Jun. 15, 2022		Oct. 01, 2017
Interest Payable date					June 15 and December 15
Line of Credit Facility [Abstract]
Line of Credit Facility, Amount Outstanding	$ 20.0	$ 302.0
Covenant terms	a ratio of total consolidated debt to consolidated EBITDA (as defined in the Amended Credit Agreement) measured for the previous twelve months of not more than 5.0 to 1.0, or up to 5.5 to 1.0 for the three quarters following an acquisition.

[1] The net proceeds of this offering were used to reduce borrowings under the Partnership's revolving credit facility.