Fair Value Measurements (Details 2) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Assets
Gross Amounts Recognized	$ 116,026	$ 89,563
Gross Amounts Offset in the Balance Sheet	(90,271)	(61,811)
Net Amounts Presented in the Balance Sheet	25,755	27,752
Margin Deposits not Offset in the Balance Sheet	(17,657)	(15,806)
Net Amounts	8,098	11,946
Liabilities
Gross Amounts Recognized	121,585	86,390
Gross Amounts Offset in the Balance Sheets	(90,271)	(61,811)
Net Amounts Presented in the Balance Sheets	31,314	24,579
Margin Deposits not Offset in the Balance Sheets	(21,865)	(17,025)
Net Amounts	9,449	7,554
Net - Amounts Presented in the Balance Sheets	(5,559)	3,173
Net - Margin Deposits not Offset in the Balance Sheets	4,208	1,219
Net	(1,351)	4,392
Commodity derivatives
Assets
Gross Amounts Recognized	113,175	88,682
Gross Amounts Offset in the Balance Sheet	(89,976)	(61,706)
Net Amounts Presented in the Balance Sheet	23,199	26,976
Margin Deposits not Offset in the Balance Sheet	(15,101)	(15,030)
Net Amounts	8,098	11,946
Liabilities
Gross Amounts Recognized	121,130	85,975
Gross Amounts Offset in the Balance Sheets	(89,976)	(61,706)
Net Amounts Presented in the Balance Sheets	31,154	24,269
Margin Deposits not Offset in the Balance Sheets	(21,705)	(16,861)
Net Amounts	9,449	7,408
Net - Amounts Presented in the Balance Sheets	(7,955)
Currency derivatives
Assets
Gross Amounts Recognized	2,851	881
Gross Amounts Offset in the Balance Sheet	(295)	(105)
Net Amounts Presented in the Balance Sheet	2,556	776
Margin Deposits not Offset in the Balance Sheet	(2,556)	(776)
Liabilities
Gross Amounts Recognized	455	415
Gross Amounts Offset in the Balance Sheets	(295)	(105)
Net Amounts Presented in the Balance Sheets	160	310
Margin Deposits not Offset in the Balance Sheets	(160)	(164)
Net Amounts		146
Net - Amounts Presented in the Balance Sheets	$ 2,396