Commitments and Contingencies (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended	6 Months Ended	12 Months Ended			3 Months Ended		12 Months Ended
	Mar. 31, 2012	Mar. 31, 2012 Cash performance unit awards	Sep. 30, 2012 Cash performance unit awards	Sep. 30, 2011 Cash performance unit awards	Sep. 30, 2010 Cash performance unit awards	Mar. 31, 2012 SARs	Dec. 31, 2011 SARs	Sep. 30, 2011 SARs
Commitments and Contingencies
Percentage of stock price on grant date							135.00%
Performance period, years					P5Y
Amount of free cash flow performance goals					$ 850.0
Amount of free cash flow achieved		256.5
Amount of free cash flow expenses accrued		2.7
Amount of free cash flow expenses accrued and unpaid		2.0
Maximum payout		27.4
Percentage of performance units vested			50.00%	50.00%
Average stock price period (in days)		P60D				P60D
Expense related solely to increase in average stock price		0.5
Average closing stock price (in dollars per share)		$ 3.41
Maximum payout under stock price method		1.2
Amount recorded for grants		2.0
Grants approved by committee to employees for cash settled stock appreciation rights (in shares)							1.0	0.4
Amount accrued for awards						0.6
Amount accrued for awards if stock price is above grant date price						0.1
Grant-date stock price (in dollars per share)						$ 1.85		$ 3.81
Threshold stock price at which SARS will vest (in dollars per share)							$ 2.50
Expenses incurred under DDCP	$ 0.2