Accrued Liabilities (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Mar. 31, 2013
Accrued Liabilities
Accrued gas purchases	$ 39,095	$ 14,213
Accrued interest	17,269	2,845
Employee-related accruals	9,801	13,836
Other accrued liabilities	6,263	8,946
Total	$ 72,428	$ 39,840