Earnings Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	May 31, 2012	May 31, 2011	May 31, 2010
Basic EPS:
Net income attributable to AAR and noncontrolling interest	$ 68,029	$ 69,826	$ 43,202
Less income attributable to participating shares	(2,545)	(2,279)
Less (income) loss attributable to noncontrolling interest	(306)		1,426
Net income attributable to AAR available to common shareholders	65,178	67,547	44,628
Basic shares:
Weighted average common shares outstanding	38,814,000	38,355,000	38,182,000
Earnings per share - basic:
Earnings per share - basic (in dollars per share)	$ 1.68	$ 1.76	$ 1.17
Diluted EPS:
Net income attributable to AAR and noncontrolling interest	68,029	69,826	43,202
Income attributable to participating shares	(2,346)
Less (income) loss attributable to noncontrolling interest	(306)		1,426
Add after-tax interest on convertible debt	5,863	5,615	5,274
Net income attributable to AAR available to common shareholders - Diluted	$ 71,240	$ 75,441	$ 49,902
Diluted shares:
Weighted average common shares outstanding	38,814,000	38,355,000	38,182,000
Additional shares from the assumed exercise of stock options	213,000	319,000	196,000
Additional shares from the assumed vesting of restricted stock		851,000	645,000
Additional shares from the assumed conversion of convertible debt	4,057,000	4,068,000	4,068,000
Weighted average common shares outstanding - diluted	43,084,000	43,593,000	43,091,000
Earnings per share - diluted:
Earnings per share - diluted (in dollars per share)	$ 1.65	$ 1.73	$ 1.16
Antidilutive stock options excluded from the computation of diluted earnings per share (in shares)	1,627,000	170,000	378,000