Net Income Per Unit (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013
Net Income Per Unit
Net income attributable to partners	$ 44,498		$ 18,678
Partners' distributions (including IDRs)	(6,847)	[1]	(1,666)	[1]
Limited partners' distributions on common units	(23,129)		(14,835)
Limited partner’s distributions on subordinated units	(9,000)		(7,475)
Allocation of distributions less (greater) than earnings	5,522		(5,298)
Weighted average limited partner units outstanding:
Common units - basic (units)	39,186,006		28,861,234
Common unit equivalents (units)	98,382		67,894
Common units - diluted (units)	39,284,388		28,929,128
Subordinated units - basic and diluted (units)	15,254,890		15,254,890
Net income per limited partner unit:
Common - basic and diluted (dollars per unit)	$ 0.64	[2]	$ 0.40	[2]
Subordinated - basic and diluted (dollars per unit)	$ 0.64	[2]	$ 0.37	[2]
Footnote
General partner’s ownership interest	2.00%		2.00%
Maximum percentage distribution to general partner	50.00%		50.00%
Minimum distribution level for IDRs	$ 0.388125		$ 0.388125
General Partner
Net Income Per Unit
Net income attributable to partners	6,836
Partners' distributions (including IDRs)	(6,847)		(1,666)
Allocation of distributions less (greater) than earnings	2,761		(107)
Total partners' earnings	9,608		1,559
Limited Partner, common units
Net Income Per Unit
Net income attributable to partners	27,109
Limited partners' distributions on common units	(23,129)		(14,835)
Allocation of distributions less (greater) than earnings	1,987		(3,396)
Total partners' earnings	25,116		11,439
Subordinated
Net Income Per Unit
Net income attributable to partners	10,553
Limited partner’s distributions on subordinated units	(9,000)		(7,475)
Allocation of distributions less (greater) than earnings	774		(1,795)
Total partners' earnings	$ 9,774		$ 5,680

[1] 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.

[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, net income per common and subordinated limited partner units will not agree for the three months ended March 31, 2013.