Derivatives (Schedule of Price Risk Derivatives) (Details)	Sep. 30, 2012
Coal Sales [Member]
Derivative [Line Items]
Derivatives Held	13,368,000
Coal Purchases [Member]
Derivative [Line Items]
Derivatives Held	3,891,000
Year One [Member] | Coal Sales [Member]
Derivative [Line Items]
Derivatives Held	2,915,000
Year One [Member] | Coal Purchases [Member]
Derivative [Line Items]
Derivatives Held	1,851,000
Year Two [Member] | Coal Sales [Member]
Derivative [Line Items]
Derivatives Held	5,713,000
Year Two [Member] | Coal Purchases [Member]
Derivative [Line Items]
Derivatives Held	1,140,000
Year Three [Member] | Coal Sales [Member]
Derivative [Line Items]
Derivatives Held	4,020,000
Year Three [Member] | Coal Purchases [Member]
Derivative [Line Items]
Derivatives Held	900,000
Year Four [Member] | Coal Sales [Member]
Derivative [Line Items]
Derivatives Held	720,000
Year Four [Member] | Coal Purchases [Member]
Derivative [Line Items]
Derivatives Held