Receivables from customers, net and notes receivable, net - Allowance for Bad Debts Rollforward (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Allowance for Doubtful Accounts Receivable [Roll Forward]
Allowance for Doubtful Accounts - Customer and Notes Receivable	$ 5.8	$ 1.2	$ 1.0
Provision for bad debts	6.0	5.3	0.2
Allowance for Doubtful Accounts Receivable, Charge-offs	(0.6)	(0.7)	0.0
Allowance for Doubtful Accounts - Customer and Notes Receivable	$ 11.2	$ 5.8	$ 1.2