Selected Quarterly Data (Unaudited) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	May 31, 2014	Feb. 28, 2014	Nov. 30, 2013	Aug. 31, 2013	May 31, 2013	Feb. 28, 2013	Nov. 30, 2012	Aug. 31, 2012	May 31, 2014	May 31, 2013	May 31, 2012
Selected Quarterly Data (Unaudited)
Sales	$ 505.4	$ 474.4	$ 540.7	$ 514.5	$ 553.8	$ 520.2	$ 512.8	$ 550.5	$ 2,035.0	$ 2,137.3	$ 2,065.0
Gross Profit	85.8	78.7	91.0	84.7	60.3	76.2	87.4	90.3	340.2	314.2	318.6
Net income attributable to AAR	$ 17.1	$ 17.9	$ 20.0	$ 17.9	$ 0.6	$ 18.4	$ 17.8	$ 18.2	$ 72.9	$ 55.0	$ 67.7
Diluted earnings per share (in dollars per share)	$ 0.43	$ 0.45	$ 0.50	$ 0.45	$ 0.01	$ 0.46	$ 0.44	$ 0.45	$ 1.83	$ 1.38
Dividends declared (in dollars per share)	$ 0.075	$ 0.075	$ 0.075	$ 0.075	$ 0.075	$ 0.075	$ 0.075	$ 0.075	$ 0.30	$ 0.30
High Market Price (in dollars per share)	$ 31.05	$ 30.56	$ 31.30	$ 25.84	$ 20.47	$ 20.11	$ 17.17	$ 14.88	$ 31.30	$ 20.47
Low Market Price (in dollars per share)	$ 24.22	$ 25.91	$ 25.51	$ 20.06	$ 16.47	$ 15.13	$ 13.55	$ 10.34	$ 20.06	$ 10.34