Selected Quarterly Data (Unaudited) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	May 31, 2013	Feb. 28, 2013	Nov. 30, 2012	Aug. 31, 2012	May 31, 2012	Feb. 29, 2012	Nov. 30, 2011	Aug. 31, 2011	May 31, 2013	May 31, 2012	May 31, 2011
Selected Quarterly Data (Unaudited)
Sales	$ 553.8	$ 520.2	$ 512.8	$ 550.5	$ 563.3	$ 534.2	$ 482.0	$ 485.5	$ 2,137.3	$ 2,065.0	$ 1,805.1
Gross profit	60.3	76.2	87.4	90.3	77.4	86.9	78.6	75.7	314.2	318.6	307.1
Net income attributable to AAR	$ 0.6	$ 18.4	$ 17.8	$ 18.2	$ 12.9	$ 20.6	$ 17.6	$ 16.6	$ 55.0	$ 67.7	$ 69.8
Diluted earnings per share-continuing operations (in dollars per share)	$ 0.01	$ 0.46	$ 0.44	$ 0.45	$ 0.32	$ 0.50	$ 0.43	$ 0.41	$ 1.38	$ 1.65
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)	$ 20.47	$ 20.11	$ 17.17	$ 14.88	$ 22.68	$ 23.37	$ 23.04	$ 31.42	$ 20.47	$ 31.42
Low Market Price (in dollars per share)	$ 16.47	$ 15.13	$ 13.55	$ 10.34	$ 12.05	$ 16.72	$ 15.17	$ 21.89	$ 10.34	$ 12.05