Earnings per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Nov. 30, 2011	Nov. 30, 2010	Nov. 30, 2011	Nov. 30, 2010
Basic EPS:
Income from continuing operations	$ 17,519	$ 18,090	$ 34,482	$ 32,137
Less income attributable to participating shares	(681)		(1,277)
Income from continuing operations available to common shareholders	16,838	18,090	33,205	32,137
Income (loss) from discontinued operations	13	(1,276)	(301)	(1,649)
Net income attributable to AAR available to common shareholders	16,851	16,814	32,904	30,488
Basic shares:
Weighted average common shares outstanding (in shares)	38,703,000	38,301,000	38,802,000	38,335,000
Earnings per share - basic:
Earnings from continuing operations (in dollars per share)	$ 0.44	$ 0.47	$ 0.86	$ 0.84
Income (Loss) from discontinued operations, net of tax (in dollars per share)	$ 0.00	$ (0.03)	$ (0.01)	$ (0.04)
Earnings per share - basic (in dollars per share)	$ 0.44	$ 0.44	$ 0.85	$ 0.80
Diluted EPS:
Income from continuing operations	17,519	18,090	34,482	32,137
Less income attributable to participating shares	(628)		(1,176)
Add after-tax interest on convertible debt	1,484	1,392	2,945	2,763
Income from continuing operations available to common shareholders	18,375	19,482	36,251	34,900
Income (loss) from discontinued operations	13	(1,276)	(301)	(1,649)
Net income attributable to AAR available to common shareholders - Diluted	$ 18,388	$ 18,206	$ 35,950	$ 33,251
Diluted shares:
Weighted average common shares outstanding (in shares)	38,703,000	38,301,000	38,802,000	38,335,000
Additional shares from the assumed exercise of stock options (in shares)	147,000	274,000	285,000	172,000
Additional shares from the assumed vesting of restricted stock (in shares)		587,000		517,000
Additional shares from the assumed conversion of convertible debt (in shares)	4,107,000	4,068,000	4,107,000	4,068,000
Weighted average common shares outstanding - diluted (in shares)	42,957,000	43,230,000	43,194,000	43,092,000
Earnings per share - diluted:
Earnings from continuing operations (in dollars per share)	$ 0.43	$ 0.45	$ 0.84	$ 0.81
Income (loss) from discontinued operations, net of tax (in dollars per share)	$ 0.00	$ (0.03)	$ (0.01)	$ (0.04)
Earnings per share - diluted (in dollars per share)	$ 0.43	$ 0.42	$ 0.83	$ 0.77
Antidilutive stock options excluded from the computation of diluted earnings per share (in shares)			267,000	449,000