Condensed Consolidated Statement Of Shareholders' Equity (USD $) In Millions	Common Stock [Member]	Additional Paid-In Capital [Member]	Common Stock In Treasury [Member]	Retained Earnings [Member]	Accum. Other Comprehensive Loss [Member]	Total
Balance at Sep. 30, 2011	$ 0.6	$ 1,957.3	$ (338.9)	$ 1,026.9	$ (80.7)	$ 2,565.2
Net earnings				87.8		87.8
Unrealized loss on securities					(21.9)	(21.9)
Benefit plan adjustment, net of $10.1 tax expense					16.6	16.6
Cash flow hedging adjustments, net of $2.3 tax expense					4.9	4.9
Foreign currency translation adjustment					12.4	12.4
Comprehensive income						99.8
Purchases of treasury stock (8 shares)			(0.6)			(0.6)
Activity under stock and deferred compensation plans (289 shares)		(3.1)	11.8			8.7
Stock-based compensation expense		7.9				7.9
Spin-off of Post cereals business				(1,012.8)	11.1	(1,001.7)
Balance at Mar. 31, 2012	$ 0.6	$ 1,962.1	$ (327.7)	$ 101.9	$ (57.6)	$ 1,679.3