Derivative Instrument and Hedging Activities 2 (Details) (USD $)	Sep. 30, 2012 Successor [Member]		Sep. 30, 2012 Successor [Member] Cash Flow Hedges: [Member]		Sep. 30, 2012 Successor [Member] Cash Flow Hedges: [Member] Interest rate contracts [Member] Derivative instruments - liabilities [Member]		Sep. 30, 2012 Successor [Member] Cash Flow Hedges: [Member] Interest rate contracts [Member] Deferred credits [Member]		Sep. 30, 2012 Successor [Member] Economic Hedges [Member]		Sep. 30, 2012 Successor [Member] Economic Hedges [Member] Interest rate contracts [Member] Derivative instruments - liabilities [Member]		Sep. 30, 2012 Successor [Member] Economic Hedges [Member] Interest rate contracts [Member] Deferred credits [Member]		Sep. 30, 2012 Successor [Member] Gathering and Processing [Member] Cash Flow Hedges: [Member] Natural gas price swaps [Member] Deferred credits [Member]	Sep. 30, 2012 Successor [Member] Gathering and Processing [Member] Cash Flow Hedges: [Member] Natural gas price swaps [Member] Prepayments and other assets [Member]		Sep. 30, 2012 Successor [Member] Gathering and Processing [Member] Cash Flow Hedges: [Member] Natural gas price swaps [Member] Accounts payable - related parties [Member]		Sep. 30, 2012 Successor [Member] Gathering and Processing [Member] Cash Flow Hedges: [Member] NGL price swaps [Member] Derivative instruments - liabilities [Member]		Sep. 30, 2012 Successor [Member] Gathering and Processing [Member] Cash Flow Hedges: [Member] NGL price swaps [Member] Prepayments and other assets [Member]		Sep. 30, 2012 Successor [Member] Gathering and Processing [Member] Economic Hedges [Member] Other derivative instruments [Member] Derivative instruments - liabilities [Member]		Sep. 30, 2012 Successor [Member] Distribution [Member] Economic Hedges [Member] Natural gas price swaps [Member] Derivative instruments - liabilities [Member]		Sep. 30, 2012 Successor [Member] Distribution [Member] Economic Hedges [Member] Natural gas price swaps [Member] Other Assets [Member]		Sep. 30, 2012 Successor [Member] Distribution [Member] Economic Hedges [Member] Natural gas price swaps [Member] Deferred credits [Member]		Dec. 31, 2011 Predecessor [Member]		Dec. 31, 2011 Predecessor [Member] Cash Flow Hedges: [Member]		Dec. 31, 2011 Predecessor [Member] Cash Flow Hedges: [Member] Interest rate contracts [Member] Derivative instruments - liabilities [Member]		Dec. 31, 2011 Predecessor [Member] Cash Flow Hedges: [Member] Interest rate contracts [Member] Deferred credits [Member]		Dec. 31, 2011 Predecessor [Member] Economic Hedges [Member]		Dec. 31, 2011 Predecessor [Member] Economic Hedges [Member] Interest rate contracts [Member] Derivative instruments - liabilities [Member]		Dec. 31, 2011 Predecessor [Member] Economic Hedges [Member] Interest rate contracts [Member] Deferred credits [Member]		Dec. 31, 2011 Predecessor [Member] Gathering and Processing [Member] Cash Flow Hedges: [Member] Natural gas price swaps [Member] Deferred credits [Member]		Dec. 31, 2011 Predecessor [Member] Gathering and Processing [Member] Cash Flow Hedges: [Member] Natural gas price swaps [Member] Prepayments and other assets [Member]		Dec. 31, 2011 Predecessor [Member] Gathering and Processing [Member] Cash Flow Hedges: [Member] Natural gas price swaps [Member] Accounts payable - related parties [Member]		Dec. 31, 2011 Predecessor [Member] Gathering and Processing [Member] Cash Flow Hedges: [Member] NGL price swaps [Member] Derivative instruments - liabilities [Member]		Dec. 31, 2011 Predecessor [Member] Gathering and Processing [Member] Cash Flow Hedges: [Member] NGL price swaps [Member] Prepayments and other assets [Member]		Dec. 31, 2011 Predecessor [Member] Gathering and Processing [Member] Economic Hedges [Member] Other derivative instruments [Member] Derivative instruments - liabilities [Member]		Dec. 31, 2011 Predecessor [Member] Distribution [Member] Economic Hedges [Member] Natural gas price swaps [Member] Derivative instruments - liabilities [Member]		Dec. 31, 2011 Predecessor [Member] Distribution [Member] Economic Hedges [Member] Natural gas price swaps [Member] Other Assets [Member]		Dec. 31, 2011 Predecessor [Member] Distribution [Member] Economic Hedges [Member] Natural gas price swaps [Member] Deferred credits [Member]
Derivative [Line Items]
Asset Derivatives	$ 6,589,000	[1]	$ 5,821,000	[1]	$ 0	[1]	$ 0	[1]	$ 768,000	[1]	$ 0	[1]	$ 0	[1]	$ 0	$ 1,498,000	[1]	$ 0	[1]	$ 0	[1]	$ 4,323,000	[1]	$ 0	[1]	$ 0	[1]	$ 768,000	[1]	$ 0	[1]	$ 6,127,000	[1]	$ 6,124,000	[1]	$ 0	[1]	$ 0	[1]	$ 3,000	[1]	$ 0	[1]	$ 0	[1]	$ 0	[1]	$ 6,124,000	[1]	$ 0	[1]	$ 0	[1]	$ 0	[1]	$ 0	[1]	$ 0	[1]	$ 0	[1]	$ 3,000	[1]
Liability Derivatives	$ 95,545,000	[1]	$ 7,135,000	[1]	$ 0	[1]	$ 0	[1]	$ 88,410,000	[1]	$ 17,310,000	[1]	$ 63,142,000	[1]	$ 0	$ 0	[1]	$ 7,135,000	[1]	$ 0	[1]	$ 0	[1]	$ 0	[1]	$ 7,958,000	[1]	$ 0	[1]	$ 0	[1]	$ 126,026,000	[1]	$ 85,865,000	[1]	$ 19,936,000	[1]	$ 59,789,000	[1]	$ 40,161,000	[1]	$ 0	[1]	$ 0	[1]	$ 0	[1]	$ 0	[1]	$ 0	[1]	$ 4,144,000	[1]	$ 1,996,000	[1]	$ 50,000	[1]	$ 34,468,000	[1]	$ 0	[1]	$ 5,643,000	[1]

[1] The Company has master netting arrangements with certain of its counterparties, which permit applicable obligations of the parties to be settled on a net versus gross basis. If a right of offset exists, the fair value amounts for the derivative instruments are reported in the unaudited interim condensed consolidated balance sheet on a net basis and disclosed herein on a gross basis.