Derivatives (Schedule of Price Risk Derivatives) (Details)	Mar. 31, 2012
Year One [Member] | Coal Sales [Member]
Derivative [Line Items]
Derivatives Held	(3,025)
Year One [Member] | Coal Purchases [Member]
Derivative [Line Items]
Derivatives Held	417
Year Two [Member] | Coal Sales [Member]
Derivative [Line Items]
Derivatives Held	(1,117)
Year Three [Member] | Coal Sales [Member]
Derivative [Line Items]
Derivatives Held	(1,440)
Year Four [Member] | Coal Sales [Member]
Derivative [Line Items]
Derivatives Held	(720)