Selected Quarterly Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	May 31, 2016	Feb. 29, 2016	Nov. 30, 2015	Aug. 31, 2015	May 31, 2015	Feb. 28, 2015	Nov. 30, 2014	Aug. 31, 2014	May 31, 2016	May 31, 2015	May 31, 2014
Sales	$ 458.2	$ 402.8	$ 423.8	$ 377.8	$ 415.8	$ 380.1	$ 403.3	$ 395.1	$ 1,662.6	$ 1,594.3	$ 1,709.1
Gross Profit	64.2	58.3	59.9	54.5	(20.4)	50.1	67.2	62.4	236.9	159.3	288.9
Income (Loss) from Continuing Operations Attributable to AAR	11.2	10.7	10.4	8.2	(82.1)	1.9	13.9	11.8	40.5	(54.5)	67.2
Income (Loss) from discontinued operations attributable to AAR	0.8	(5.9)	(2.4)	14.7	97.2	(36.4)	1.3	2.6	7.2	64.7	5.7
Net income (loss) attributable to AAR	$ 12.0	$ 4.8	$ 8.0	$ 22.9	$ 15.1	$ (34.5)	$ 15.2	$ 14.4	$ 47.7	$ 10.2	$ 72.9
Earnings (Loss) per share - basic:
Earnings (Loss) from continuing operations	$ 0.32	$ 0.31	$ 0.30	$ 0.23	$ (2.12)	$ 0.05	$ 0.35	$ 0.29	$ 1.16	$ (1.40)	$ 1.70
Earnings (Loss) from discontinued operations	0.03	(0.17)	(0.07)	0.42	2.50	(0.94)	0.03	0.07	0.21	1.66	0.15
Earnings per share - basic	0.35	0.14	0.23	0.65	0.38	(0.89)	0.38	0.36	1.37	0.26	1.85
Earnings (Loss) per share - diluted:
Earnings (Loss) from continuing operations	0.32	0.31	0.30	0.23	(2.12)	0.05	0.35	0.29	1.16	(1.40)	1.68
Earnings (Loss) from discontinued operations	0.02	(0.17)	(0.07)	0.42	2.48	(0.94)	0.03	0.07	0.21	1.64	0.15
Earnings (Loss) per share-diluted	$ 0.34	$ 0.14	$ 0.23	$ 0.65	$ 0.36	$ (0.89)	$ 0.38	$ 0.36	$ 1.37	$ 0.24	$ 1.83
Pre-tax gain on sale of business (net of transaction expenses and fees)									$ 27.7	$ 198.6
Pre- tax impairment charges and other losses					$ 71.4
Loss on extinguishment of debt					44.9				$ 0.4	$ 44.9
Precision Systems Manufacturing
Earnings (Loss) per share - diluted:
Impairment of Precision Systems Manufacturing					11.1	$ 46.4
Impairment of net assets					11.1	$ 46.4
Telair Cargo Group
Earnings (Loss) per share - diluted:
Pre-tax gain on sale of business (net of transaction expenses and fees)				$ 27.7	$ 198.6