Note 15 - Stock-based Compensation (Tables)

9 Months Ended

May 31, 2017

Notes Tables

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]

Three months ended	May 31, 2017				May 31, 2016
Term structure of risk-free interest rate		0.49%	-	1.89%		0.40%	-	1.90%
Expected life (years)			7.4				7.5
Term structure of volatility		21%	-	29%		24%	-	30%
Dividend yield			1.18%				1.33%
Weighted average estimated fair value			$42.23				$40.57
Weighted average exercise price			$163.05				$152.10
Fair value as a percentage of exercise price			25.9%				26.7%

Nine months ended	May 31, 2017				May 31, 2016
Term structure of risk-free interest rate		0.07%	-	2.09%		0.07%	-	2.12%
Expected life (years)			7.4				7.7
Term structure of volatility		21%	-	30%		21%	-	30%
Dividend yield			1.18%				1.09%
Weighted average estimated fair value			$39.98				$46.05
Weighted average exercise price			$154.01				$168.51
Fair value as a percentage of exercise price			26.0%				27.3%

The 2008 Employee Stock Purchase Plan [Member]

Notes Tables

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]

Three months ended	May 31, 2017			May 31, 2016
Risk-free interest rate		0.81	%		0.27	%
Expected life (months)		3			3
Expected volatility		8.3	%		11.53	%
Dividend yield		1.24	%		1.29	%
Weighted average estimated fair value	$	29.84		$	26.07

Nine months ended	May 31, 2017			May 31, 2016
Risk-free interest rate		0.56	%		0.20	%
Expected life (months)		3			3
Expected volatility		8.7	%		11.42	%
Dividend yield		1.21	%		1.15	%
Weighted average estimated fair value	$	28.48		$	27.19

Non Employee Directors Stock Option Plan [Member]

Notes Tables

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]

Risk-free interest rate	1.95	%
Expected life (years)	5.4
Expected volatility	22.7	%
Dividend yield	1.24	%

Risk-free interest rate	1.62	%
Expected life (years)	5.4
Expected volatility	23.0	%
Dividend yield	1.05	%