Unaudited Quarterly Results (Details) - USD ($) $ / shares in Units, $ 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
Quarterly Financial Information Disclosure [Abstract]
Net sales	$ 1,755.4		$ 1,747.5	$ 1,524.3	$ 1,252.0	$ 1,578.3		$ 1,612.3	$ 1,554.2		$ 1,353.3		$ 6,279.2	$ 6,098.1	$ 6,808.2
Gross income	299.1		314.6	259.3	182.8	249.7		284.0	275.8		229.7		1,055.8	1,039.2	1,182.7
Operating income	95.5		146.8	91.4	30.3	86.6		136.6	109.7		65.7		364.0	398.6	503.3
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 (loss) attributable to Oshkosh Corporation common shareholders
Less: net 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
Earnings per share attributable to common shareholders:
Total earnings (loss) per share-basic (in dollars per share)	$ 0.83		$ 1.15	$ 0.77	$ 0.20	$ 0.65		$ 1.15	$ 0.70		$ 0.44		$ 2.94	$ 2.94	$ 3.66
Earnings per share-diluted:
Total earnings (loss) per share -diluted (in dollars per share)	0.82		1.13	0.76	0.19	0.64		1.13	0.69		0.43		$ 2.91	$ 2.90	$ 3.61
Common Stock per share dividends (in dollars per share)	$ 0.19		$ 0.19	$ 0.19	$ 0.19	$ 0.17		$ 0.17	$ 0.17		$ 0.17

[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).