Consolidated Statement Of Changes In Partners' Capital (USD $) In Thousands	Predecessor's Capital [Member]	Class C Convertible Preferred [Member]	General Partner [Member]	Limited Partners-Public Common [Member]	Limited Partners-Affiliated - Common [Member]	Limited Partners-Affiliated - Subordinated [Member]	Total
Balances at Dec. 21, 2010	$ 304,540						$ 304,540
Initial public offering				279,750			279,750
Deferred tax benefit as a result of IPO				134	101	64	299
Distributions to the Predecessor			(2)	(779)	(506)	(320)
Contributions from general partner			715				715
Contributions from the Predecessor	52,579						52,579
Distribution to the Fund					(183,767)	(116,233)	(300,000)
Proceeds from unit offering				279,750			279,750
Other contributions from affiliates	644				113	71	828
Recognition of unit-based awards				20			20
Book value of assets contributed by the Predecessor	(223,736)				137,051	86,685
Net income (loss)	(4,938)		(7)	(3,181)	(2,396)	(1,515)	(12,037)
Balances at Dec. 31, 2010	129,089		708	276,723	(48,898)	(30,928)	326,694
Distributions to the Predecessor			(15)	(7,186)	(4,660)	(2,948)
Balances at Mar. 31, 2011
Balances at Dec. 31, 2010	129,089		708	276,723	(48,898)	(30,928)	326,694
Distributions to the Predecessor	(25,507)						(25,507)
Proceeds from over-allotment				41,963			41,963
Distribution to the Fund					(25,727)	(16,273)	(42,000)
Other contributions from affiliates	17,357				12,366	7,822	37,545
Units issued to the General Partner				41,963			41,963
Recognition of unit-based awards				1,351			1,351
Reduction in units to cover individuals' tax withholding				(215)			(215)
Distributions to unitholders		3,424	63	30,673	19,854	12,557	66,571
Book value of assets contributed by the Predecessor	(249,331)						(249,331)
Fair value of Preferred Units issued to the Fund		354,500					354,500
Fair value of Preferred Units in excess of net assets received from the Fund			(102)	(49,491)	(32,380)	(20,481)	(102,454)
Amortization of discount on increasing rate distributions		3,638					3,638
Noncash distribution to preferred unitholders		(3,638)					(3,638)
Management incentive fee earned			1,572				1,572
Net income (loss)	76,249	7,062	1,575	1,648	1,079	682	88,295
Balances at Dec. 31, 2011	(52,143)	358,138	546	241,306	(113,414)	(71,735)	362,698
Balances at Sep. 30, 2011
Distributions to the Predecessor		(3,424)	(16)	(8,344)	(5,368)	(3,393)
Fair value of Preferred Units issued to the Fund		354,500
Balances at Dec. 31, 2011		358,138	546	241,306	(113,414)	(71,735)
Distributions to the Predecessor		(3,500)	(20)	(17,892)		(3,394)
Balances at Mar. 31, 2012
Balances at Dec. 31, 2011	(52,143)	358,138	546	241,306	(113,414)	(71,735)	362,698
Initial public offering			272	376,938			377,210
Distributions to the Predecessor	(37,270)						(37,270)
Proceeds from unit offering			272	376,938			377,210
Other contributions from affiliates	6,485				4,985	26,606	38,076
Recognition of unit-based awards				3,252			3,252
Reduction in units to cover individuals' tax withholding				322			322
Distributions to unitholders		(14,000)	(60)	(55,005)		(10,362)	(79,427)
Conversion of subordinated units					(53,122)	53,122
Book value of assets contributed by the Predecessor	(45,578)						(45,578)
Fair value of Preferred Units issued to the Fund							354,500
Amortization of discount on increasing rate distributions		14,930					14,930
Noncash distribution to preferred unitholders		(14,930)					(14,930)
Affiliated unit sale to the public				(113,325)	113,325
Consideration paid in excess of transferred properties received			(59)	(60,390)	(8,412)		(68,861)
Management incentive fee earned			(6,121)				(6,121)
Net income (loss)	37,350	28,930	6,132	11,303	(6,333)	2,369	79,751
Balances at Dec. 31, 2012		373,068	710	403,757	(62,971)		714,564
Balances at Sep. 30, 2012
Distributions to the Predecessor		(3,500)	(25)	(25,275)	(3,484)
Balances at Dec. 31, 2012		$ 373,068	$ 710	$ 403,757	$ (62,971)