Receivables - Impaired loans (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
Recorded investment	$ 103.8	$ 80.7
Unpaid principal face	104.2	80.8
Related allowance	75.1	63.4
Average recorded investment	92.3	79.1
Interest income recognized on impaired loans	1.1	0.5
Contracts [Member]
Recorded investment	28.3	5.7
Unpaid principal face	28.7	5.8
Related allowance	14.6	2.6
Average recorded investment	17.0	4.1
Notes [Member]
Recorded investment	75.5	75.0
Unpaid principal face	75.5	75.0
Related allowance	60.5	60.8
Average recorded investment	$ 75.3	$ 75.0