Note 15 - Employee Stock Option and Retirement Plans - Exercise Price Ranges of Outstanding and Exercisable Options (Details) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Aug. 31, 2018 USD ($) $ / shares shares
Number Outstanding (in shares) | shares	3,143
Outstanding Weighted Average Remaining Years of Contractual Life (Year)
Outstanding Weighted Average Exercise Price Per Share (in dollars per share)
Outstanding Aggregate Intrinsic Value | $	$ 2,399,684
Exercisable Number Exercisable (in shares) | shares	1,022
Exercisable Weighted Average Exercise Price Per Share (in dollars per share)
Exercisable Aggregate Intrinsic Value | $	$ 105,297
Range 1 [Member]
Range of Exercise Prices Per Share, Lower Limit (in dollars per share)	$ 87.26
Range of Exercise Prices Per Share, Upper Limit (in dollars per share)	$ 92.22
Number Outstanding (in shares) | shares	333
Outstanding Weighted Average Remaining Years of Contractual Life (Year)	3 years 328 days
Outstanding Weighted Average Exercise Price Per Share (in dollars per share)	$ 91.75
Outstanding Aggregate Intrinsic Value | $	$ 45,794
Exercisable Number Exercisable (in shares) | shares	333
Exercisable Weighted Average Exercise Price Per Share (in dollars per share)	$ 91.75
Exercisable Aggregate Intrinsic Value | $	$ 45,794
Range 2 [Member]
Range of Exercise Prices Per Share, Lower Limit (in dollars per share)	$ 94.84
Range of Exercise Prices Per Share, Upper Limit (in dollars per share)	$ 110.31
Number Outstanding (in shares) | shares	180
Outstanding Weighted Average Remaining Years of Contractual Life (Year)	4 years 36 days
Outstanding Weighted Average Exercise Price Per Share (in dollars per share)	$ 99.24
Outstanding Aggregate Intrinsic Value | $	$ 23,459
Exercisable Number Exercisable (in shares) | shares	137
Exercisable Weighted Average Exercise Price Per Share (in dollars per share)	$ 98.18
Exercisable Aggregate Intrinsic Value | $	$ 17,914
Range 3 [Member]
Range of Exercise Prices Per Share, Lower Limit (in dollars per share)	$ 131.31
Range of Exercise Prices Per Share, Upper Limit (in dollars per share)	$ 148.52
Number Outstanding (in shares) | shares	403
Outstanding Weighted Average Remaining Years of Contractual Life (Year)	6 years 36 days
Outstanding Weighted Average Exercise Price Per Share (in dollars per share)	$ 134.93
Outstanding Aggregate Intrinsic Value | $	$ 38,071
Exercisable Number Exercisable (in shares) | shares	173
Exercisable Weighted Average Exercise Price Per Share (in dollars per share)	$ 131.54
Exercisable Aggregate Intrinsic Value | $	$ 16,889
Range 4 [Member]
Range of Exercise Prices Per Share, Lower Limit (in dollars per share)	$ 150.81
Range of Exercise Prices Per Share, Upper Limit (in dollars per share)	$ 152.28
Number Outstanding (in shares) | shares	637
Outstanding Weighted Average Remaining Years of Contractual Life (Year)	8 years 36 days
Outstanding Weighted Average Exercise Price Per Share (in dollars per share)	$ 152.25
Outstanding Aggregate Intrinsic Value | $	$ 49,139
Exercisable Number Exercisable (in shares) | shares	124
Exercisable Weighted Average Exercise Price Per Share (in dollars per share)	$ 152.23
Exercisable Aggregate Intrinsic Value | $	$ 9,551
Range 5 [Member]
Range of Exercise Prices Per Share, Lower Limit (in dollars per share)	$ 159.14
Range of Exercise Prices Per Share, Upper Limit (in dollars per share)	$ 170.24
Number Outstanding (in shares) | shares	627
Outstanding Weighted Average Remaining Years of Contractual Life (Year)	7 years 292 days
Outstanding Weighted Average Exercise Price Per Share (in dollars per share)	$ 165.23
Outstanding Aggregate Intrinsic Value | $	$ 40,227
Exercisable Number Exercisable (in shares) | shares	110
Exercisable Weighted Average Exercise Price Per Share (in dollars per share)	$ 163.55
Exercisable Aggregate Intrinsic Value | $	$ 7,262
Range 6 [Member]
Range of Exercise Prices Per Share, Lower Limit (in dollars per share)	$ 171.22
Range of Exercise Prices Per Share, Upper Limit (in dollars per share)	$ 175.20
Number Outstanding (in shares) | shares	383
Outstanding Weighted Average Remaining Years of Contractual Life (Year)	7 years 73 days
Outstanding Weighted Average Exercise Price Per Share (in dollars per share)	$ 175.06
Outstanding Aggregate Intrinsic Value | $	$ 20,816
Exercisable Number Exercisable (in shares) | shares	145
Exercisable Weighted Average Exercise Price Per Share (in dollars per share)	$ 175.06
Exercisable Aggregate Intrinsic Value | $	$ 7,887
Range 7 [Member]
Range of Exercise Prices Per Share, Lower Limit (in dollars per share)	$ 189.98
Range of Exercise Prices Per Share, Upper Limit (in dollars per share)	$ 200.20
Number Outstanding (in shares) | shares	580
Outstanding Weighted Average Remaining Years of Contractual Life (Year)	9 years 73 days
Outstanding Weighted Average Exercise Price Per Share (in dollars per share)	$ 190.68
Outstanding Aggregate Intrinsic Value | $	$ 22,462
Exercisable Number Exercisable (in shares) | shares
Exercisable Weighted Average Exercise Price Per Share (in dollars per share)
Exercisable Aggregate Intrinsic Value | $