Accrued Liabilities (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Accrued Liabilities
Accrued gas purchases	$ 75,454	$ 14,213
Employee-related accruals	22,315	13,836
Accrued interest	2,037	2,845
Other accrued liabilities	11,312	8,946
Total	$ 111,118	$ 39,840