Allowance For Doubtful Accounts (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2009
Allowance For Doubtful Accounts [Abstract]
Balance, beginning of year	$ 1.1	$ 2.0	$ 0.4
Provision charged to expense		(0.9)	2.1
Write-offs, less recoveries	(0.1)	(0.3)	0.1
Transfers to/from Ralcorp Receivables Corporation	1.1	0.3	(0.6)
Balance, end of year	$ 2.1	$ 1.1	$ 2.0