Earnings Per Share (Details) - USD ($) $ in Millions	3 Months Ended												12 Months Ended
	Sep. 30, 2016	[1]	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	[2]	Jun. 30, 2015	Mar. 31, 2015	[3]	Dec. 31, 2014	[4]	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Amount attributable to Oshkosh Corporation common shareholders:
Net income	$ 61.5		$ 84.2	$ 56.1	$ 14.6	$ 50.3		$ 89.9	$ 54.6		$ 34.7		$ 216.4	$ 229.5	$ 309.3
Earnings allocated to participating securities						(0.1)		(0.2)	(0.1)		(0.1)		0.0	(0.5)	(1.2)
Earnings available to common shareholders						$ 50.2		$ 89.7	$ 54.5		$ 34.6		$ 216.4	$ 229.0	$ 308.1
Weighted-average common shares outstanding (in shares)													73,570,020	77,990,432	84,123,949
Dilutive stock options and other equity-based compensation awards (in shares)													862,898	1,101,303	1,540,287
Participating stock awards (in shares)													0	(110,317)	(206,601)
Diluted weighted-average common shares outstanding (in shares)													74,432,918	78,981,418	85,457,635

[1] The fourth quarter of fiscal 2016 was impacted by a combined $27.8 million ($17.5 million after-tax) asset impairment and workforce reduction charge in the access equipment segment

[2] The fourth quarter of fiscal 2015 was impacted by a combined $2.9 million ($2.4 million after-tax) workforce reduction charge in the access equipment segment and corporate.

[3] The second quarter of fiscal 2015 was impacted by a $14.7 million ($9.3 million after-tax) charge for debt extinguishment costs related to refinancing portions of the Company's long-term debt.

[4] The first quarter of fiscal 2015 was impacted by a $3.4 million ($2.1 million after-tax) pension curtailment benefit in connection with staffing reductions in the defense segment as a result of declining sales to the DoD (See Note 17 of the Notes to Consolidated Financial Statements).