Note 14 - Stock-based Compensation (Tables)

6 Months Ended

Feb. 28, 2019

Notes Tables

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

Three months ended February 28,	2019					2018
Term structure of risk-free interest rate		2.48%	-	3.14	%		1.28%	-	2.41	%
Expected life (years)				7.1					7.4
Term structure of volatility		18%	-	25	%		19%	-	29	%
Dividend yield				1.15	%				1.32	%
Weighted average estimated fair value	$	53.18				$	48.82
Weighted average exercise price	$	207.84				$	192.11
Fair value as a percentage of exercise price				25.6	%				25.4	%

Six months ended February 28,	2019					2018
Term structure of risk-free interest rate		1.28%	-	3.14	%		1.28%	-	2.41	%
Expected life (years)				7.1					7.4
Term structure of volatility		18%	-	29	%		19%	-	29	%
Dividend yield				1.16	%				1.32	%
Weighted average estimated fair value	$	56.72				$	48.29
Weighted average exercise price	$	221.74				$	190.04
Fair value as a percentage of exercise price				25.6	%				25.4	%

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 28,	2019			2018
Risk-free interest rate		2.42	%		1.45	%
Expected life (months)		3			3
Expected volatility		12.47	%		13.9	%
Dividend yield		1.09	%		1.11	%
Weighted average estimated fair value	$	40.45		$	35.02

Six months ended February 28,	2019			2018
Risk-free interest rate		2.35	%		1.26	%
Expected life (months)		3			3
Expected volatility		10.68	%		10.52	%
Dividend yield		1.10	%		1.29	%
Weighted average estimated fair value	$	39.52		$	29.76

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	2.51	%
Expected life (years)	5.4
Expected volatility	20.5	%
Dividend yield	1.17	%

Risk-free interest rate	2.34	%
Expected life (years)	5.4
Expected volatility	19.7	%
Dividend yield	1.16	%