Fair Value Measurement (Narrative) (Details)	9 Months Ended
	Mar. 31, 2012
Unobservable Price Component, as a percent	100.00%
Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Commodity Derivative Contracts [Member] | Weighted Average [Member] | Assets [Member]
Basis	15.10%
Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Commodity Derivative Contracts [Member] | Weighted Average [Member] | Liabilities [Member]
Basis	24.10%