Fair Value Measurements (Tables)

6 Months Ended

Mar. 31, 2012

Fair Value Measurements [Abstract]

Assets And Liabilities Measured At Fair Value On Recurring Basis

	March 31, 2012						September 30, 2011
	Total		Level 1		Level 2		Total		Level 1		Level 2
Assets
Marketable securities	$	.8	$	.8	$	—	$	8.2	$	8.2	$	—
Investment in Post Holdings, Inc.		223.1		223.1				—		—		—
Derivative assets		1.5		—		1.5		.3		—		.3
Deferred compensation investment		25.0		25.0		—		22.9		22.9		—
	$	250.4	$	248.9	$	1.5	$	31.4	$	31.1	$	.3
Liabilities
Derivative liabilities	$	24.7	$	—	$	24.7	$	53.1	$	—	$	53.1
Deferred compensation liabilities		30.3		—		30.3		36.5		—		36.5
	$	55.0	$	—	$	55.0	$	89.6	$	—	$	89.6