Debt Obligations - Narrative (Details) (USD $)			12 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Dec. 31, 2013 Southern Union Credit Facility [Member]	Mar. 31, 2013 Southern Union Credit Facility [Member]	Mar. 31, 2013 Line of Credit [Member]	Dec. 31, 2012 Line of Credit [Member]	Mar. 31, 2013 Panhandle [Member] Term Loan due 2015 [Member]
Debt Instrument [Line Items]
Long-term Debt, Fair Value	$ 3,430,000,000	$ 3,390,000,000
Long-term debt	3,300,000,000	3,280,000,000					455,000,000
Line of Credit Facility, Maximum Borrowing Capacity				700,000,000
Line of Credit Facility, Expiration Date			May 01, 2016
Debt, Weighted Average Interest Rate				1.83%			1.83%
Line of Credit Facility, Amount Outstanding					$ 240,000,000	$ 210,000,000