Supplemental Guarantor / Non-Guarantor Financial Information Condensed Consolidating Statement of Comprehensive Income (Details) (USD $) In Thousands, unless otherwise specified	1 Months Ended	3 Months Ended							12 Months Ended
	Dec. 31, 2011	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011		Dec. 31, 2010
Revenues [Abstract]
Affiliates									$ 245,582	$ 168,261		$ 146,367
Third parties									46,978	46,007	[1]	35,770	[1]
Total revenues	69,087	81,431	74,054	68,660	68,415	49,151	50,908	45,122	292,560	214,268	[1]	182,137	[1]
Operating costs and expenses [Abstract]
Operating Costs and Expenses									89,242	64,521	[1]	54,946	[1]
Depreciation and amortization									57,461	36,958	[1]	31,363	[1]
General and administrative									7,594	6,576	[1]	7,719	[1]
Operating Expenses									154,297	108,055	[1]	94,028	[1]
Operating income (loss)	36,705	40,973	35,572	30,116	31,602	20,598	26,648	22,262	138,263	106,213	[1]	88,109	[1]
Equity in earnings of SLC Pipeline									3,364	2,552	[1]	2,393	[1]
Interest expense									(47,182)	(35,959)		(33,994)
Other expense									10	17	[1]	17	[1]
Loss on early extinguishment of debt									(2,979)	0	[1]	0	[1]
Other									10			17
Other nonoperating income (expense) and equity earnings									(46,787)	(33,390)	[1]	(31,584)	[1]
Income before income taxes	27,560	28,932	23,909	19,204	19,431	12,431	18,391	14,441	91,476	72,823	[1]	56,525	[1]
State income tax expense									(371)	(234)		(296)
Income (Loss) from Continuing Operations, Including Portion Attributable to Noncontrolling Interest	27,495	28,848	23,773	19,128	19,356	12,508	18,373	14,213	91,105	72,589	[1]	56,229	[1]
Operating costs of acquired assets for period prior to acquisition									4,200	6,351	[1]	70	[1]
Allocation of Net Income (Loss) Attributable to Noncontrolling Interest									(1,153)	859	[1]	24	[1]
Net Income (Loss) Attributable to Parent	30,894	27,039	23,336	22,003	21,774	15,632	18,673	14,600	94,152	79,799	[1]	56,323	[1]
Other comprehensive income (loss)									2,185	3,562	[1]	(885)	[1]
Comprehensive Income									96,337	83,361		55,438
Comprehensive Income (Loss) net of Noncontrolling Interest									96,337	83,361		55,438
Subsidiaries [Member]
Operating costs and expenses [Abstract]
Income (Loss) from Equity Method Investments									0	0		0
SLC Pipeline [Member]
Operating costs and expenses [Abstract]
Equity in earnings of SLC Pipeline									3,364	2,552		2,393
Parent [Member]
Revenues [Abstract]
Affiliates									0	0		0
Third parties									0	0		0
Total revenues									0	0		0
Operating costs and expenses [Abstract]
Operating Costs and Expenses									0	0		0
Depreciation and amortization									0	0		0
General and administrative									3,336	3,902		5,053
Operating Expenses									3,336	3,902		5,053
Operating income (loss)									(3,336)	(3,902)		(5,053)
Interest expense									(31,523)	(24,494)		(23,358)
Other expense										0
Loss on early extinguishment of debt									(2,979)
Other									0			0
Other nonoperating income (expense) and equity earnings									96,241	77,350		61,306
Income before income taxes									92,905	73,448		56,253
State income tax expense									0	0		0
Income (Loss) from Continuing Operations, Including Portion Attributable to Noncontrolling Interest									92,905	73,448		56,253
Operating costs of acquired assets for period prior to acquisition									4,200	6,351		70
Allocation of Net Income (Loss) Attributable to Noncontrolling Interest									(2,953)	0		0
Net Income (Loss) Attributable to Parent									94,152	79,799		56,323
Other comprehensive income (loss)									2,185	3,562		(885)
Comprehensive Income									96,337	83,361		55,438
Parent [Member] | Subsidiaries [Member]
Operating costs and expenses [Abstract]
Income (Loss) from Equity Method Investments									130,743	101,844		84,664
Parent [Member] | SLC Pipeline [Member]
Operating costs and expenses [Abstract]
Equity in earnings of SLC Pipeline									0	0		0
Guarantor Subsidiaries [Member]
Revenues [Abstract]
Affiliates									232,986	168,519		146,391
Third parties									41,984	46,005		35,762
Total revenues									274,970	214,524		182,153
Operating costs and expenses [Abstract]
Operating Costs and Expenses									78,766	63,100		54,755
Depreciation and amortization									43,147	35,200		31,476
General and administrative									4,258	2,674		2,666
Operating Expenses									126,171	100,974		88,897
Operating income (loss)									148,799	113,550		93,256
Interest expense									(15,659)	(11,465)		(10,636)
Other expense										17
Loss on early extinguishment of debt									0
Other									10			17
Other nonoperating income (expense) and equity earnings									(17,685)	(11,472)		(8,296)
Income before income taxes									131,114	102,078		84,960
State income tax expense									(371)	(234)		(296)
Income (Loss) from Continuing Operations, Including Portion Attributable to Noncontrolling Interest									130,743	101,844		84,664
Operating costs of acquired assets for period prior to acquisition									0	0		0
Allocation of Net Income (Loss) Attributable to Noncontrolling Interest									0	0		0
Net Income (Loss) Attributable to Parent									130,743	101,844		84,664
Other comprehensive income (loss)									0	0		0
Comprehensive Income									130,743	101,844		84,664
Guarantor Subsidiaries [Member] | Subsidiaries [Member]
Operating costs and expenses [Abstract]
Income (Loss) from Equity Method Investments									(5,400)	(2,576)		(70)
Guarantor Subsidiaries [Member] | SLC Pipeline [Member]
Operating costs and expenses [Abstract]
Equity in earnings of SLC Pipeline									3,364	2,552		2,393
Non-Guarantor Subsidiaries [Member]
Revenues [Abstract]
Affiliates									13,754	313		0
Third parties									4,994	2		8
Total revenues									18,748	315		8
Operating costs and expenses [Abstract]
Operating Costs and Expenses									11,634	1,992		215
Depreciation and amortization									14,314	1,758		(113)
General and administrative									0	0		0
Operating Expenses									25,948	3,750		102
Operating income (loss)									(7,200)	(3,435)		(94)
Interest expense									0	0		0
Other expense										0
Loss on early extinguishment of debt									0
Other									0			0
Other nonoperating income (expense) and equity earnings									0	0		0
Income before income taxes									(7,200)	(3,435)		(94)
State income tax expense									0	0		0
Income (Loss) from Continuing Operations, Including Portion Attributable to Noncontrolling Interest									(7,200)	(3,435)		(94)
Operating costs of acquired assets for period prior to acquisition									0	0		0
Allocation of Net Income (Loss) Attributable to Noncontrolling Interest									0	0		0
Net Income (Loss) Attributable to Parent									(7,200)	(3,435)		(94)
Other comprehensive income (loss)									0	0		0
Comprehensive Income									(7,200)	(3,435)		(94)
Non-Guarantor Subsidiaries [Member] | Subsidiaries [Member]
Operating costs and expenses [Abstract]
Income (Loss) from Equity Method Investments									0	0		0
Non-Guarantor Subsidiaries [Member] | SLC Pipeline [Member]
Operating costs and expenses [Abstract]
Equity in earnings of SLC Pipeline									0	0		0
Eliminations [Member]
Revenues [Abstract]
Affiliates									(1,158)	(571)		(24)
Third parties									0	0		0
Total revenues									(1,158)	(571)		(24)
Operating costs and expenses [Abstract]
Operating Costs and Expenses									(1,158)	(571)		(24)
Depreciation and amortization									0	0		0
General and administrative									0	0		0
Operating Expenses									(1,158)	(571)		(24)
Operating income (loss)									0	0		0
Interest expense									0	0		0
Other expense										0
Loss on early extinguishment of debt									0
Other									0			0
Other nonoperating income (expense) and equity earnings									(125,343)	(99,268)		(84,594)
Income before income taxes									(125,343)	(99,268)		(84,594)
State income tax expense									0	0		0
Income (Loss) from Continuing Operations, Including Portion Attributable to Noncontrolling Interest									(125,343)	(99,268)		(84,594)
Operating costs of acquired assets for period prior to acquisition									0	0		0
Allocation of Net Income (Loss) Attributable to Noncontrolling Interest									1,800	859		24
Net Income (Loss) Attributable to Parent									(123,543)	(98,409)		(84,570)
Other comprehensive income (loss)									0	0		0
Comprehensive Income									(123,543)	(98,409)		(84,570)
Eliminations [Member] | Subsidiaries [Member]
Operating costs and expenses [Abstract]
Income (Loss) from Equity Method Investments									(125,343)	(99,268)		(84,594)
Eliminations [Member] | SLC Pipeline [Member]
Operating costs and expenses [Abstract]
Equity in earnings of SLC Pipeline									$ 0	$ 0		$ 0

[1] (1) Restated as described in Note 2.