Employee Retirement Plans (Details 1)	3 Months Ended		12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2009	Sep. 30, 2008
Pension Benefit [Member]
Weighted-average assumption:
Discount rate	5.50%	5.00%	5.30%	5.00%	5.50%	6.80%
Expected return on plan assets			8.00%	8.50%	8.50%	8.50%
Rate of interest in salary levels			3.50%	3.80%	3.80%	3.80%
Other Postretirement Benefits [Member]
Weighted-average assumption:
Discount rate			5.30%	5.00%	5.50%	6.80%
Expected return on plan assets			5.50%	5.50%	5.50%	5.50%
Rate of interest in salary levels			3.50%	3.80%	3.80%	3.80%