Segment Information (Details 1) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Segment Reporting Information [Line Items]
Sales to external customers	$ 351,194	$ 525,735	$ 722,903	$ 1,015,505
Purchased gas and NGLs	260,890	429,177	532,846	829,111
Operating expenses	30,571	27,913	58,378	52,957
Gain (loss) on derivatives	(4,905)	1,536	(2,736)	4,957
Depreciation Depletion Amortization And Impairment	(32,889)	(31,654)	(65,085)	(61,326)
Identifiable assets	2,248,437		2,248,437		1,962,616
LIG Operating Segments [Member]
Segment Reporting Information [Line Items]
Sales to external customers	121,479	219,479	268,177	424,397
Sales to affiliates	60,415	23,728	133,225	46,050
Purchased gas and NGLs	(153,601)	(211,417)	(342,822)	(406,920)
Operating expenses	(8,759)	(8,902)	(16,696)	(16,969)
Segment profit	19,534	22,888	41,884	46,558
Gain (loss) on derivatives	4,541	1,269	4,643	(3,954)
Depreciation Depletion Amortization And Impairment	(3,200)	(4,045)	(6,372)	(7,205)
Capital expenditures	1,886	1,129	1,888	2,679
Identifiable assets	280,090	327,174	280,090	327,174
NTX Operating Segments [Member]
Segment Reporting Information [Line Items]
Sales to external customers	61,236	87,813	125,917	168,779
Sales to affiliates	17,227	21,295	48,711	42,880
Purchased gas and NGLs	(31,457)	(64,360)	(81,478)	(127,519)
Operating expenses	(14,144)	(12,108)	(27,295)	(23,460)
Segment profit	32,862	32,640	65,855	60,680
Gain (loss) on derivatives	(153)	377	(2,416)	(1,094)
Depreciation Depletion Amortization And Impairment	(21,009)	(18,744)	(41,442)	(36,464)
Capital expenditures	20,295	16,807	33,451	35,011
Identifiable assets	1,086,299	1,112,750	1,086,299	1,112,750
PNGL Operating Segments [Member]
Segment Reporting Information [Line Items]
Sales to external customers	168,479	218,443	328,809	422,329
Sales to affiliates	40,243	207	85,787	692
Purchased gas and NGLs	(193,717)	(198,630)	(376,269)	(384,294)
Operating expenses	(7,668)	(6,903)	(14,387)	(12,528)
Segment profit	7,337	13,117	23,940	26,199
Gain (loss) on derivatives	517	(110)	509	91
Depreciation Depletion Amortization And Impairment	(8,069)	(7,828)	(16,028)	(15,541)
Capital expenditures	30,255	5,555	45,917	9,636
Identifiable assets	498,888	492,920	498,888	492,920
Corporate Elimination [Member]
Segment Reporting Information [Line Items]
Sales to external customers	0	0	0	0
Sales to affiliates	(117,885)	(45,230)	(267,723)	(89,622)
Purchased gas and NGLs	117,885	45,230	267,723	89,622
Operating expenses	0	0	0	0
Segment profit	0	0	0	0
Gain (loss) on derivatives	0	0	0	0
Depreciation Depletion Amortization And Impairment	(611)	(1,037)	(1,243)	(2,116)
Capital expenditures	1,076	715	1,536	1,202
Identifiable assets	$ 383,160	$ 78,345	$ 383,160	$ 78,345