Earnings per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Feb. 29, 2012	Feb. 28, 2011	Feb. 29, 2012	Feb. 28, 2011
Basic EPS:
Net income attributable to AAR and noncontrolling interest	$ 20,835	$ 17,918	$ 55,016	$ 48,406
Less income attributable to participating shares	(805)		(2,072)
Less income attributable to noncontrolling interest	(172)		(172)
Net income attributable to AAR available to common shareholders	19,858	17,918	52,772	48,406
Basic shares:
Weighted average common shares outstanding	38,650,000	38,361,000	38,753,000	38,341,000
Earnings per share - basic:
Earnings per share - basic (in dollars per share)	$ 0.51	$ 0.47	$ 1.36	$ 1.26
Diluted EPS:
Net income attributable to AAR and noncontrolling interest	20,835	17,918	55,016	48,406
Less income attributable to participating shares	(738)		(1,905)
Less income attributable to noncontrolling interest	(172)		(172)
Add after-tax interest on convertible debt	1,508	1,415	4,453	4,178
Net income attributable to AAR available to common shareholders - Diluted	$ 21,433	$ 19,333	$ 57,392	$ 52,584
Diluted shares:
Weighted average common shares outstanding	38,650,000	38,361,000	38,753,000	38,341,000
Additional shares from the assumed exercise of stock options	208,000	496,000	259,000	283,000
Additional shares from the assumed vesting of restricted stock		788,000		766,000
Additional shares from the assumed conversion of convertible debt	4,122,000	4,068,000	4,122,000	4,068,000
Weighted average common shares outstanding - diluted	42,980,000	43,713,000	43,134,000	43,458,000
Earnings per share - diluted:
Earnings per share - diluted (in dollars per share)	$ 0.50	$ 0.44	$ 1.33	$ 1.21
Antidilutive stock options excluded from the computation of diluted earnings per share (in shares)			260,000	278,000