Share-based payments (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended		1 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Nov. 30, 2010 Minimum [Member] Date of 2013 Earnings Release [Member] Restricted Stock [Member]	Oct. 31, 2010 Minimum [Member] Date of 2013 Earnings Release [Member] Restricted Stock [Member]	Nov. 30, 2010 Maximum [Member] Date of 2013 Earnings Release [Member] Restricted Stock [Member]	Oct. 31, 2010 Maximum [Member] Date of 2013 Earnings Release [Member] Restricted Stock [Member]	Nov. 30, 2010 Third Anniversary of Grant [Member] Restricted Stock [Member]	Oct. 31, 2010 Third Anniversary of Grant [Member] Restricted Stock [Member]	Nov. 30, 2010 Date of 2013 Earnings Release [Member] Restricted Stock [Member]	Oct. 31, 2010 Date of 2013 Earnings Release [Member] Restricted Stock [Member]	Oct. 31, 2010 Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation Cost	$ 9.3	$ 7.1	$ 27.4	$ 22.1
Tax Benefit from Compensation Expense	$ 3.5	$ 2.6	$ 10.2	$ 8.1
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period									47,900	86,700	111,700	202,300	313,300
Vesting Amount if EPS CAGR is Achieved											100.00%	100.00%
Minimum EPS CAGR Required For Full Vesting											12.00%	12.00%
EPS CAGR Threshold For Vesting Percentages Less Than Full Amount					5.00%	5.00%	12.00%	12.00%