Equity (Details 3) (USD $) In Thousands, except Share data, unless otherwise specified	0 Months Ended														12 Months Ended
	Apr. 25, 2013	Feb. 04, 2013	Jan. 24, 2013	Oct. 29, 2012	Oct. 17, 2012	Aug. 03, 2012	Jul. 24, 2012	Apr. 30, 2012	Apr. 18, 2012	Feb. 03, 2012	Jan. 24, 2012	Oct. 31, 2011	Oct. 21, 2011	Jul. 25, 2011	Mar. 31, 2013	Mar. 31, 2012
Distributions
First level cash distribution percentage to holders of common units															99.90%
First level cash distribution percentage to general partner															0.10%
Second level cash distribution percentage to holders of subordinated units															99.90%
Second level cash distribution percentage to general partner															0.10%
Third level cash distribution percentage to general partner															0.10%
Distributions
Distributions to partners prior to initial public offering																$ 3,850
Distribution declared per unit (in dollars per unit)																$ 0.35
Amount per unit (in dollars per unit)	$ 0.4775		$ 0.4625		$ 0.4500		$ 0.4125		$ 0.3625		$ 0.3500		$ 0.3375	$ 0.1669
Number of equivalent units that were not eligible to receive a distribution		1,202,085		516,978		17,862,470		3,932,031		7,117,031		4,000,000
Minimum
Distributions
Total Quarterly Distribution per Unit (in dollars per unit)															0.3375
First target distribution | Minimum
Distributions
Total Quarterly Distribution per Unit (in dollars per unit)															0.3375
First target distribution | Maximum
Distributions
Total Quarterly Distribution per Unit (in dollars per unit)															0.388125
Second target distribution | Minimum
Distributions
Total Quarterly Distribution per Unit (in dollars per unit)															0.388125
Second target distribution | Maximum
Distributions
Total Quarterly Distribution per Unit (in dollars per unit)															0.421875
Third target distribution | Minimum
Distributions
Total Quarterly Distribution per Unit (in dollars per unit)															0.421875
Third target distribution | Maximum
Distributions
Total Quarterly Distribution per Unit (in dollars per unit)															0.50625
Thereafter | Minimum
Distributions
Total Quarterly Distribution per Unit (in dollars per unit)															0.50625
Limited Partners
Distributions
Marginal Percentage Interest In Distributions															99.90%
Amount Paid to Limited Partners	25,605		24,245		22,846		13,574		9,165		7,735		4,990	2,467
Limited Partners | First target distribution
Distributions
Marginal Percentage Interest In Distributions															99.90%
Limited Partners | Second target distribution
Distributions
Marginal Percentage Interest In Distributions															86.90%
Limited Partners | Third target distribution
Distributions
Marginal Percentage Interest In Distributions															76.90%
Limited Partners | Thereafter
Distributions
Marginal Percentage Interest In Distributions															51.90%
General Partner
Distributions
Marginal Percentage Interest In Distributions															0.10%
Distributions to partners prior to initial public offering																4
Amount Paid to General Partner	$ 1,189		$ 927		$ 707		$ 134		$ 10		$ 10		$ 5	$ 3
General Partner | Minimum
Distributions
Annual incentive distributions to general partner (in dollars per unit)															1.35
Total Quarterly Distribution per Unit (in dollars per unit)															0.3375
General Partner | First target distribution
Distributions
Marginal Percentage Interest In Distributions															0.10%
General Partner | Second target distribution
Distributions
Marginal Percentage Interest In Distributions															13.10%
General Partner | Third target distribution
Distributions
Marginal Percentage Interest In Distributions															23.10%
General Partner | Thereafter
Distributions
Marginal Percentage Interest In Distributions															48.10%