Note 14 - Stock-based Compensation (Tables)

6 Months Ended

Feb. 29, 2016

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	February 29, 2016			February 28, 2015
Risk-free interest rate		0.26	%		0.03	%
Expected life (months)		3			3
Expected volatility		12.5	%		8.1	%
Dividend yield		1.03	%		1.13	%

Six months ended	February 29, 2016			February 28, 2015
Risk-free interest rate		0.17	%		0.02	%
Expected life (months)		3			3
Expected volatility		11.4	%		8.3	%
Dividend yield		1.08	%		1.17	%

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	1.62	%
Expected life (years)	5.4
Expected volatility	23.0	%
Dividend yield	1.05	%

Risk-free interest rate	1.45	%
Expected life (years)	5.4
Expected volatility	23.5	%
Dividend yield	1.30	%

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

Three months ended	February 29, 2016				February 28, 2015
Term structure of risk-free interest rate		0.16%	-	2.12%		0.06%	-	2.34%
Expected life (years)			7.42				8.3
Term structure of volatility		21%	-	30%		21%	-	31%
Dividend yield			1.07%				1.29%
Weighted average estimated fair value			$40.51				$43.05
Weighted average exercise price			$150.81				$147.05
Fair value as a percentage of exercise price			26.9%				29.3%

Six months ended	February 29, 2016				February 28, 2015
Term structure of risk-free interest rate		0.07%	-	2.12%		0.06%	-	2.34%
Expected life (years)			7.77				8.2
Term structure of volatility		21%	-	30%		21%	-	31%
Dividend yield			1.07%				1.35%
Weighted average estimated fair value			$46.59				$39.07
Weighted average exercise price			$170.13				$135.40
Fair value as a percentage of exercise price			27.4%				28.9%