Derivative Instrument and Hedging Activities - Narrative (Details) (USD $) In Millions, unless otherwise specified								3 Months Ended
	Mar. 31, 2013 Term Loan Due March 2012 [Member]	Dec. 31, 2011 Successor [Member] Southern Union [Member] Junior Subordinated Debt [Member]	Mar. 31, 2013 Interest Rate Swap [Member]	Dec. 31, 2011 Interest Rate Swap [Member]	Dec. 31, 2011 Interest Rate Swap [Member] Interest Rate Swap, Ten Year Period [Member]	Dec. 31, 2011 Interest Rate Swap [Member] Interest Rate Swap, Five Year Period [Member]	Mar. 31, 2013 Interest Rate Swap [Member] LIBOR [Member] Junior Subordinated Debt [Member]	Mar. 31, 2013 Natural gas price swaps [Member] Gathering and Processing [Member]	Mar. 31, 2013 Natural gas price swaps [Member] Year 2013 [Member] MMBtus [Member] Gathering and Processing [Member] MMbtu	Mar. 31, 2013 Natural gas price swaps [Member] Year 2013 [Member] MMBtus [Member] Distribution [Member] MMbtu	Mar. 31, 2013 Natural gas price swaps [Member] Year 2014 [Member] MMBtus [Member] Distribution [Member] MMbtu	Mar. 31, 2013 Natural gas price swaps [Member] Year 2015 [Member] MMBtus [Member] Distribution [Member] MMbtu
Derivative [Line Items]
Derivative notional amount			$ 455	$ 525	$ 450	$ 75
Debt instrument, three month LIBOR, basis spread on variable rate							3.0175%
Interest rate swap, period (in years)					10 years	5 years
Derivative fixed interest rate			3.63%
Derivative notional amount, nonmonetary (in MMBtu or gallons)									3,437,500	14,030,000	8,160,000	220,000
Debt, face amount	455	600
Net, after-tax losses in accumulated other comprehensive income								$ 3