Earnings (Loss) Per Share (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Amount attributable to Oshkosh Corporation common shareholders:
Net income from continuing operations	$ 46.5	$ 39.0
Less: net earnings allocated to participating securities	(0.3)	(0.1)
Net income available to Oshkosh Corporation common shareholders	46.2	38.9
Net income (loss) from discontinued operations	$ 0	$ (0.1)
Basic weighted-average shares outstanding (in shares)	90,303,191	91,186,347
Effect of dilutive stock options and other equity-based compensation awards (in shares)	878,606	585,278
Diluted weighted-average shares outstanding (in shares)	91,181,797	91,771,625
Common Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti dilutive options outstanding excluded from earnings per share calculation (in shares)	2,087,728	3,255,629