Discontinued Operations (Details) (USD $)	12 Months Ended
	Sep. 30, 2014 item	Sep. 30, 2013	Sep. 30, 2012	Jan. 31, 2013
Discontinued operations
Gain (loss) on disposal	$ 2,000,000
Income (loss) from discontinued operations, net of income taxes	(415,000)	(1,148,000)	(35,819,000)
Reversal of unrecognized tax benefits in discontinued operations resulting from IRS audit		2,700,000
Number of reclamation obligations	1
Coal Cleaning Business
Discontinued operations
Remaining assets held for sale				0
Revenue	0	4,386,000	22,268,000
Loss from operations of discontinued operations before income taxes	(3,175,000)	(3,752,000)	(36,210,000)
Gain (loss) on disposal	2,727,000	(55,000)	267,000
Income tax provision	33,000	2,659,000	124,000
Income (loss) from discontinued operations, net of income taxes	(415,000)	(1,148,000)	(35,819,000)
Impairment charges related to coal cleaning business			13,000,000
Reversal of unrecognized tax benefits in discontinued operations resulting from IRS audit		2,700,000
Deferred purchase price and royalty payments received	4,700,000
Number of sales transactions in which the buyer agreed to assume the lease and certain reclamation obligations	1
Number of reclamation obligations	1
Accrued contingent liability for reclamation obligations	$ 8,000,000