Financing Arrangements (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended	1 Months Ended	9 Months Ended
	Jun. 30, 2012 Revolving credit agreement Y	May 31, 2012 Revolving credit agreement terminated May 2012 Y	Jun. 30, 2012 Secured letter of credit facility agreement Y
Financial arrangement
Term under revolving credit agreement (in years)	5	5
Maximum borrowing capacity under revolving credit agreement	$ 200	$ 150
Letters of credit outstanding	26.8		57.7
Available amount under line of credit	173.2
Collateral in a restricted account			68.7
Maximum amount of letters of credit currently allowed by the facility			$ 66.7
Initial term under the letters of credit facility (in years)			1