Discontinued Operations (Details) (USD $)	12 Months Ended
	Sep. 30, 2013 item T	Sep. 30, 2012 item	Sep. 30, 2011	Jan. 31, 2013
Discontinued operations
Remaining assets held for sale	$ 0	$ 5,864,000
Loss from discontinued operations, net of income taxes	(1,148,000)	(35,819,000)	(95,989,000)
Coal cleaning business
Discontinued operations
Property, plant and equipment, held for sale		1,900,000
Other assets, held for sale		5,900,000
Remaining assets held for sale				0
Revenue	4,386,000	22,268,000	48,476,000
Loss from operations of discontinued operations before income taxes	(3,752,000)	(36,210,000)	(91,615,000)
Gain (loss) on disposal	(55,000)	267,000	0
Income tax benefit (provision)	2,659,000	124,000	(4,374,000)
Loss from discontinued operations, net of income taxes	(1,148,000)	(35,819,000)	(95,989,000)
Impairment charges related to coal cleaning business		13,000,000	72,000,000
Number of facilities sold	10	1
Cash proceeds from sale of asset		2,000,000
Maximum potential future consideration	50,000,000
Accrued contingent liability for assumed reclamation obligations	$ 6,700,000
Feedstock agreed to be identified by the entity under the obligation (in tons)	1,000,000
Number of facilities sold with which the entity has an agreement to identify feedstock	1
Liability for unidentified feedstock supply guaranteed under obligation (in dollars per ton)	7