Acquisitions (Details 6) (High Sierra, Pecos, and Third Coast acquistions, USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Pro Forma Results of Operations
Revenues	$ 5,430,449	$ 4,789,040
Income from continuing operations	56,366	15,720
Common units
Pro Forma Results of Operations
Basic earnings (FROM CONTINUING OPERATIONS) (in dollars per unit)	$ 1.00	$ 0.29
Diluted earnings (FROM CONTINUING OPERATIONS) (in dollars per unit)	$ 1.00	$ 0.29
Subordinated units
Pro Forma Results of Operations
Basic earnings (FROM CONTINUING OPERATIONS) (in dollars per unit)	$ 1.00	$ 0.29
Diluted earnings (FROM CONTINUING OPERATIONS) (in dollars per unit)	$ 1.00	$ 0.29
Limited Partners
Pro Forma Results of Operations
Income from continuing operations	$ 53,442	$ 15,704