Note 15 - Stock Option and Retirement Plans - Summary of Stock Option Activity (Details) - $ / shares	3 Months Ended												12 Months Ended
	Aug. 31, 2017	May 31, 2017	Feb. 28, 2017	Nov. 30, 2016	Aug. 31, 2016	May 31, 2016	Feb. 28, 2016	Nov. 30, 2015	Aug. 31, 2015	May 31, 2015	Feb. 28, 2015	Nov. 30, 2014	Aug. 31, 2017	Aug. 31, 2016	Aug. 31, 2015
Balance (in shares)				3,364,000				3,117,000				3,482,000	3,364,000	3,117,000	3,482,000
Balance (in dollars per share)				$ 129.54				$ 100.71				$ 79.67	$ 129.54	$ 100.71	$ 79.67
Weighted average exercise price (in dollars per share)													$ 156.77	$ 168.55	$ 141.84
Exercised (in shares)													(487,000)	(681,000)	(1,060,000)
Exercised (in dollars per share)													$ 86.17	$ 71.52	$ 63.03
Forfeited (in shares)													(539,000)	(268,000)	(134,000)
Forfeited (in dollars per share)													$ 160.31	$ 113.70	$ 106.01
Balance (in shares)	3,366,000				3,364,000				3,117,000				3,366,000	3,364,000	3,117,000
Balance (in dollars per share)	$ 139.29				$ 129.54				$ 100.71				$ 139.29	$ 129.54	$ 100.71
Balance (in dollars per share)	$ 139.29			$ 129.54	$ 129.54			$ 100.71	$ 100.71			$ 79.67	$ 129.54	$ 100.71	$ 79.67
Non Performance Based [Member]
Granted (in shares)	29,650	11,604		671,263		103,903	4,073	513,785	128,090	61,210	25,075	462,913	713,000	622,000	677,000
Weighted average exercise price (in dollars per share)													$ 152.89	$ 171.18	$ 140.49
Performance Shares [Member]
Granted (in shares)	206,417		61,744	22,460	20,911			530,418			137,522		291,000	551,000	138,000
Weighted average exercise price (in dollars per share)													$ 166.29	$ 165.59	$ 148.52
Non-Employee Director Grant [Member]
Granted (in shares)													24,000	23,000	14,000
Weighted average exercise price (in dollars per share)													$ 170.24	$ 146.82	$ 138.48