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, 2019 USD ($) $ / shares shares
Number Outstanding (in shares) | shares	2,524
Outstanding Aggregate Intrinsic Value | $	$ 261,505
Exercisable Number Exercisable (in shares) | shares	874
Exercisable Aggregate Intrinsic Value | $	$ 116,075
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	184
Outstanding Weighted Average Remaining Years of Contractual Life (Year)	2 years 11 months 23 days
Outstanding Weighted Average Exercise Price Per Share (in dollars per share)	$ 91.86
Outstanding Aggregate Intrinsic Value | $	$ 33,175
Exercisable Number Exercisable (in shares) | shares	184
Exercisable Weighted Average Exercise Price Per Share (in dollars per share)	$ 91.86
Exercisable Aggregate Intrinsic Value | $	$ 33,175
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	88
Outstanding Weighted Average Remaining Years of Contractual Life (Year)	2 years 10 months 20 days
Outstanding Weighted Average Exercise Price Per Share (in dollars per share)	$ 99.70
Outstanding Aggregate Intrinsic Value | $	$ 15,102
Exercisable Number Exercisable (in shares) | shares	88
Exercisable Weighted Average Exercise Price Per Share (in dollars per share)	$ 99.70
Exercisable Aggregate Intrinsic Value | $	$ 15,102
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	280
Outstanding Weighted Average Remaining Years of Contractual Life (Year)	5 years 3 days
Outstanding Weighted Average Exercise Price Per Share (in dollars per share)	$ 134.18
Outstanding Aggregate Intrinsic Value | $	$ 38,636
Exercisable Number Exercisable (in shares) | shares	156
Exercisable Weighted Average Exercise Price Per Share (in dollars per share)	$ 136.38
Exercisable Aggregate Intrinsic Value | $	$ 21,134
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	470
Outstanding Weighted Average Remaining Years of Contractual Life (Year)	7 years 1 month 13 days
Outstanding Weighted Average Exercise Price Per Share (in dollars per share)	$ 152.25
Outstanding Aggregate Intrinsic Value | $	$ 56,307
Exercisable Number Exercisable (in shares) | shares	150
Exercisable Weighted Average Exercise Price Per Share (in dollars per share)	$ 152.25
Exercisable Aggregate Intrinsic Value | $	$ 18,007
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	299
Outstanding Weighted Average Remaining Years of Contractual Life (Year)	6 years 1 month 2 days
Outstanding Weighted Average Exercise Price Per Share (in dollars per share)	$ 164.99
Outstanding Aggregate Intrinsic Value | $	$ 32,050
Exercisable Number Exercisable (in shares) | shares	98
Exercisable Weighted Average Exercise Price Per Share (in dollars per share)	$ 164.19
Exercisable Aggregate Intrinsic Value | $	$ 10,612
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	254
Outstanding Weighted Average Remaining Years of Contractual Life (Year)	6 years 2 months 15 days
Outstanding Weighted Average Exercise Price Per Share (in dollars per share)	$ 175.04
Outstanding Aggregate Intrinsic Value | $	$ 24,715
Exercisable Number Exercisable (in shares) | shares	124
Exercisable Weighted Average Exercise Price Per Share (in dollars per share)	$ 175.04
Exercisable Aggregate Intrinsic Value | $	$ 11,989
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	475
Outstanding Weighted Average Remaining Years of Contractual Life (Year)	8 years 2 months 15 days
Outstanding Weighted Average Exercise Price Per Share (in dollars per share)	$ 190.73
Outstanding Aggregate Intrinsic Value | $	$ 38,637
Exercisable Number Exercisable (in shares) | shares	73
Exercisable Weighted Average Exercise Price Per Share (in dollars per share)	$ 190.45
Exercisable Aggregate Intrinsic Value | $	$ 5,985
Range 8 [Member]
Range of Exercise Prices Per Share, Lower Limit (in dollars per share)	$ 200.99
Range of Exercise Prices Per Share, Upper Limit (in dollars per share)	$ 286.74
Number Outstanding (in shares) | shares	474
Outstanding Weighted Average Remaining Years of Contractual Life (Year)	9 years 2 months 4 days
Outstanding Weighted Average Exercise Price Per Share (in dollars per share)	$ 223.79
Outstanding Aggregate Intrinsic Value | $	$ 22,883
Exercisable Number Exercisable (in shares) | shares	1
Exercisable Weighted Average Exercise Price Per Share (in dollars per share)	$ 221.88
Exercisable Aggregate Intrinsic Value | $	$ 71