Risk Management Activities and Financial Instruments (Details 4) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Mar. 31, 2013
Risk management activities and financial instruments
Fiscal year ending March 31, 2014	$ 20,814
Fiscal year ending March 31, 2015	2,455
Fiscal year ending March 31, 2016	(235)
Thereafter	255
Total	23,289	3,173
Energy Contracts
Risk management activities and financial instruments
Fiscal year ending March 31, 2014	19,744
Fiscal year ending March 31, 2015	2,278
Fiscal year ending March 31, 2016	(391)
Thereafter	164
Total	21,795	2,707
Currency contracts
Risk management activities and financial instruments
Fiscal year ending March 31, 2014	1,070
Fiscal year ending March 31, 2015	177
Fiscal year ending March 31, 2016	156
Thereafter	91
Total	$ 1,494	$ 466