Share-based payments (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended				1 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013 Restricted Stock [Member]	Dec. 31, 2013 Subsequent Event [Member]	Nov. 30, 2013 Subsequent Event [Member] Restricted Stock [Member] Employee [Member] Ratably Over Four Years [Member]	Nov. 30, 2013 Subsequent Event [Member] Restricted Stock [Member] Management [Member] Third Anniversary of Grant [Member]	Nov. 30, 2013 Subsequent Event [Member] Restricted Stock [Member] Management [Member] Date of 2016 Earnings Release [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense	$ 8.3	$ 6.3
Tax Benefit from Compensation Expense	$ 3.1	$ 2.3
Restricted Stock Grants in Period					179,800	39,800	238,600
Restrcited stock vesting period			4 years
Share Price				$ 101.56
Performance share fair value - percentage premium to closing stock price			5.00%