Quarterly Financial Data (Unaudited) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	5 Months Ended	7 Months Ended	12 Months Ended	1 Months Ended	3 Months Ended						7 Months Ended	12 Months Ended	2 Months Ended	3 Months Ended	5 Months Ended	12 Months Ended
	May 25, 2010	Dec. 31, 2010	Dec. 31, 2009	Jun. 30, 2010 Successor [Member]	Dec. 31, 2011 Successor [Member]	Sep. 30, 2011 Successor [Member]	Jun. 30, 2011 Successor [Member]	Mar. 31, 2011 Successor [Member]	Dec. 31, 2010 Successor [Member]	Sep. 30, 2010 Successor [Member]	Dec. 31, 2010 Successor [Member]	Dec. 31, 2011 Successor [Member]	May 25, 2010 Predecessor [Member]	Mar. 31, 2010 Predecessor [Member]	May 25, 2010 Predecessor [Member]	Dec. 31, 2009 Predecessor [Member]
Segment Reporting Information [Line Items]
Operating Revenues	$ 24,200	$ 9,500	$ 46,200	$ 96,980	$ 369,881	$ 390,267	$ 356,498	$ 317,252	$ 322,745	$ 296,888	$ 716,613	$ 1,433,898	$ 200,265	$ 304,785	$ 505,050	$ 1,043,277
Operating income (Loss)				(1,256)	13,215	13,616	4,820	8,058	16,742	(927)	14,559	39,709	1,726	18,405	20,131	226,574
(Loss) income from continuing operations				(4,981)					(7,269)	7,522	(4,728)	73,619	(5,081)	462	(4,619)	142,758
(Loss) income from discontinued operations				86					(1,654)	324	(1,244)	0	585	(912)	(327)	(2,269)
Net income (loss) attributable to Regency Energy Partners LP				$ (4,924)	$ 13,524	$ 30,300	$ 14,544	$ 14,074	$ (8,992)	$ 7,788	$ (6,128)	$ 72,442	$ (4,740)	$ (612)	$ (5,352)	$ 140,398
Basic income from continuing operations per common unit											$ (0.10)	$ 0.39			$ (0.10)	$ 1.61
Diluted income from continuing operations per common unit											$ (0.10)	$ 0.32			$ (0.10)	$ 1.60
Basic and diluted (loss) income from continuing operations per common unit				$ (0.05)					$ (0.07)	$ 0.03			$ (0.07)	$ (0.02)
Basic and diluted (loss) income from discontinued operations per common unit				$ 0.00					$ (0.01)	$ 0.00			$ 0.01	$ (0.01)
Basic net income per common unit					$ 0.06	$ 0.18	$ 0.08	$ 0.08			$ (0.09)	$ 0.39			$ (0.10)	$ 1.63
Diluted net income per common unit					$ 0.06	$ 0.09	$ 0.07	$ 0.07			$ (0.09)	$ 0.32			$ (0.10)	$ 1.63
Basic and diluted net (loss) income per common unit				$ (0.05)					$ (0.09)	$ 0.04			$ (0.07)	$ (0.03)