Fair Value Measurements (Fair Value Heirarchy Table) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Mar. 31, 2012
Assets, Fair Value Disclosure [Abstract]
Oil derivative contracts	$ 4,376	$ 19,513
Liabilities, Fair Value Disclosure [Abstract]
Oil derivative contracts	(23,232)	(26,440)
Total	(18,856)	(6,927)
Quoted Prices in Active Markets (Level 1) [Member]
Assets, Fair Value Disclosure [Abstract]
Oil derivative contracts	0	0
Liabilities, Fair Value Disclosure [Abstract]
Oil derivative contracts	0	0
Total	0	0
Significant Other Observable Inputs (Level 2) [Member]
Assets, Fair Value Disclosure [Abstract]
Oil derivative contracts	4,376	19,513
Liabilities, Fair Value Disclosure [Abstract]
Oil derivative contracts	(23,232)	(26,440)
Total	(18,856)	(6,927)
Significant Unobservable Inputs (Level 3) [Member]
Assets, Fair Value Disclosure [Abstract]
Oil derivative contracts	0	0
Liabilities, Fair Value Disclosure [Abstract]
Oil derivative contracts	0	0
Total	$ 0	$ 0