Subsequent Events (Details) (USD $)	12 Months Ended		0 Months Ended	12 Months Ended	0 Months Ended
	Mar. 31, 2014	Mar. 31, 2014 Carlyle/Riverstone Funds	Mar. 31, 2014 Subsequent events	Mar. 31, 2014 Subsequent events Carlyle/Riverstone Funds	May 01, 2014 Subsequent events Old agreement with TransCanada MMcf	May 01, 2014 Subsequent events New agreement with TransCanada MMcf
Subsequent events
Volume of storage capacity (in million cubic feet)					40,000	40,000
Interval option period after which agreement can be terminated					5 years
Reduced volume of storage capacity after three years (in billion cubic feet)						20,000
Distribution declared and paid to common unitholders			$ 12,800,000
Additional common units issued under DRIP				445,144
Non cash earnings distribution and reinvestments	$ 18,270,000	$ 18,300,000		$ 6,400,000