Net Income Per Unit (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013
Net Income Per Unit
Net income attributable to partners	$ 32,766		$ 19,173		$ 77,264		$ 37,851
Limited partners' distributions	33,840		23,959		65,969		46,269
Allocation of distributions greater than earnings	(9,366)		(6,935)		(3,844)		(12,233)
Weighted average limited partner units outstanding:
Common units - basic	46,911,533		30,752,989		43,070,111		29,812,337
Common unit equivalents	100,891		110,149		99,187		91,443
Common units - diluted	47,012,424		30,863,138		43,169,298		29,903,780
Subordinated units - basic and diluted	7,543,627	[1]	15,254,890	[1]	11,377,957	[1]	15,254,890	[1]
Net income per limited partner unit:
Common - basic	$ 0.45	[2]	$ 0.38	[2]	$ 1.15	[2]	$ 0.77	[2]
Common - diluted	$ 0.45	[2]	$ 0.38	[2]	$ 1.14	[2]	$ 0.77	[2]
Subordinated - basic and diluted	$ 0.45	[2]	$ 0.36	[2]	$ 1.13	[2]	$ 0.73	[2]
Footnote
General partner's ownership interest	2.00%		2.00%		2.00%		2.00%
Maximum percentage distribution to general partner	50.00%		50.00%		50.00%		50.00%
Minimum distribution level for IDRs (dollars per unit)	$ 0.388125		$ 0.388125		$ 0.388125		$ 0.388125
Subordinated units effective conversion Date					May 16, 2014
Subordinated units converted into common units					0
General Partner
Net Income Per Unit
Net income attributable to partners					14,794
General partner's distributions	8,292	[3]	2,149	[3]	15,139	[3]	3,815	[3]
Allocation of distributions greater than earnings	(186)		(139)		(77)		(245)
Total partner's earnings	8,106		2,010		15,062		3,570
Footnote
Subordinated units converted into common units					0
Limited Partner, common units
Net Income Per Unit
Net income attributable to partners					48,681
Limited partners' distributions	29,199		16,179		52,328		31,014
Allocation of distributions greater than earnings	(7,908)		(4,543)		(2,980)		(7,930)
Total partner's earnings	21,291		11,636		49,348		23,084
Footnote
Subordinated units converted into common units					15,254,890
Limited Partner, subordinated units
Net Income Per Unit
Net income attributable to partners					13,789
Limited partners' distributions	4,641	[1]	7,780	[1]	13,641	[1]	15,255	[1]
Allocation of distributions greater than earnings	(1,272)	[1]	(2,253)	[1]	(787)	[1]	(4,058)	[1]
Total partner's earnings	$ 3,369	[1]	$ 5,527	[1]	$ 12,854	[1]	$ 11,197	[1]
Footnote
Subordinated units converted into common units					(15,254,890)

[1] On May 16, 2014, the 15,254,890 subordinated units were converted into common units on a one-for-one basis and thereafter participate on terms equal with all other common units in distributions of available cash. Distributions and the Partnership’s net income were allocated to the subordinated units through May 15, 2014.

[2] We base our calculation of net income per unit on the weighted-average number of common and subordinated limited partner units outstanding during the period. Therefore, as a result of the public offering of common units in January 2013, and the conversion of the subordinated units to common units in May 2014, net income per common and subordinated limited partner units may not agree for the periods presented

[3] General partner’s distributions (including IDRs) consist of an approximate 2% general partner interest and IDRs, which entitle the general partner to receive increasing percentages, up to 50%, of quarterly distributions in excess of $0.388125 per unit per quarter. See Note K of our Annual Report on Form 10-K for the year ended December 31, 2013 for further discussion related to IDRs.