Segment Disclosures (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended		12 Months Ended
	Sep. 30, 2013 item	Sep. 30, 2012 item	Sep. 30, 2013 item	Sep. 30, 2012 item	Mar. 31, 2013 item
Segment Disclosures
Number of reportable segment	1	1	1	1	1
Segment disclosures
Total revenues	$ 36,863	$ 24,545	$ 94,051	$ 21,758
Long-lived assets	1,249,029		1,249,029		1,270,024
U.S.
Segment disclosures
Net realized revenues	11,282	18,817	19,775	30,736
Net unrealized revenues	(6,146)	(12,716)	6,308	(28,093)
Long-lived assets	404,082		404,082		411,420
Canada
Segment disclosures
Net realized revenues	39,213	34,419	67,790	70,902
Net unrealized revenues	(7,486)	(15,975)	178	(51,787)
Long-lived assets	$ 844,947		$ 844,947		$ 858,604