Consolidated Balance Sheets (Parenthetical) (Unaudited) (USD $) In Millions, except Share data, unless otherwise specified	Mar. 31, 2013	Sep. 30, 2012
Statement of Financial Position [Abstract]
Valuation allowance for deferred income taxes	$ 23.2	$ 41.9
Preferred stock, par value	$ 0.1	$ 0.1
Preferred stock, shares authorized	30,000,000	30,000,000
Preferred stock, shares issued	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	1,000,000,000	1,000,000,000
Common stock, shares issued	329,455,450	328,092,047
Common stock, shares outstanding	322,255,379	320,891,976
Treasury stock, shares	7,200,071	7,200,071