Segment Information (Details Textuals) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Segment Reporting Information [Line Items]
Sales to external customers	$ 1,655,851	$ 2,013,942	$ 1,792,676
Purchased gas, NGLs and crude oil	1,262,093	1,638,777	1,454,376
Operating expenses	130,882	111,778	105,060
Loss on derivatives	1,006	7,776	9,100
Depreciation, amortization and impairments	(162,300)	(125,358)	(112,936)
Identifiable assets	2,426,475	1,962,616	1,991,103
Lig Operating Segments [Member]
Segment Reporting Information [Line Items]
Sales to external customers	561,389	811,216	880,336
Sales to affiliates	225,542	128,130	82,688
Purchased gas, NGLs and crude oil	(678,188)	(809,471)	(845,627)
Operating expenses	(33,817)	(35,434)	(33,188)
Segment profit	74,926	94,441	84,209
Loss on derivatives	3,440	(6,145)	(3,664)
Depreciation, amortization and impairments	(13,936)	(13,676)	(12,382)
Capital expenditures	4,059	2,820	9,930
Identifiable assets	279,755	305,359	331,261
Ntx Operating Segments [Member]
Segment Reporting Information [Line Items]
Sales to external customers	269,302	332,026	309,771
Sales to affiliates	96,177	100,527	89,752
Purchased gas, NGLs and crude oil	(180,116)	(262,708)	(240,085)
Operating expenses	(55,582)	(48,807)	(46,384)
Segment profit	129,781	121,038	113,054
Loss on derivatives	(4,405)	(1,896)	(5,352)
Depreciation, amortization and impairments	(83,492)	(76,535)	(64,458)
Capital expenditures	45,235	73,069	31,678
Identifiable assets	1,057,504	1,113,431	1,107,279
Pngl Operating Segments [Member]
Segment Reporting Information [Line Items]
Sales to external customers	717,123	870,700	602,569
Sales to affiliates	145,569	40,185	0
Purchased gas, NGLs and crude oil	(788,803)	(835,440)	(541,104)
Operating expenses	(29,601)	(27,537)	(25,488)
Segment profit	44,288	47,908	35,977
Loss on derivatives	(41)	265	(84)
Depreciation, amortization and impairments	(57,652)	(31,271)	(31,661)
Capital expenditures	182,782	25,618	5,871
Identifiable assets	632,962	460,865	493,143
Orv Operating Segments [Member]
Segment Reporting Information [Line Items]
Sales to external customers	108,037	0	0
Sales to affiliates	0	0	0
Purchased gas, NGLs and crude oil	(82,274)	0	0
Operating expenses	(11,882)	0	0
Segment profit	13,881	0	0
Loss on derivatives	0
Depreciation, amortization and impairments	(4,861)	0	0
Capital expenditures	3,893	0	0
Identifiable assets	316,927	0	0
Intersegment Elimination [Member]
Segment Reporting Information [Line Items]
Sales to external customers	0	0	0
Sales to affiliates	(467,288)	(268,842)	(172,440)
Purchased gas, NGLs and crude oil	467,288	268,842	172,440
Operating expenses	0	0	0
Segment profit	0	0	0
Loss on derivatives	0	0	0
Depreciation, amortization and impairments	(2,359)	(3,876)	(4,435)
Capital expenditures	8,944	2,629	1,907
Identifiable assets	139,327	82,961	59,420
Total Segment [Member]
Segment Reporting Information [Line Items]
Sales to external customers	1,655,851	2,013,942	1,792,676
Sales to affiliates	0	0	0
Purchased gas, NGLs and crude oil	(1,262,093)	(1,638,777)	(1,454,376)
Operating expenses	(130,882)	(111,778)	(105,060)
Segment profit	262,876	263,387	233,240
Loss on derivatives	(1,006)	(7,776)	(9,100)
Depreciation, amortization and impairments	(162,300)	(125,358)	(112,936)
Capital expenditures	244,913	104,136	49,386
Identifiable assets	$ 2,426,475	$ 1,962,616	$ 1,991,103