Stock-Based Compensation - Schedule of Employee Service Share-Based Compensation, Allocation of Recognized Period Costs (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Feb. 28, 2013	Feb. 29, 2012	Feb. 28, 2013	Feb. 29, 2012
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense			$ 812	$ 446
Total stock-based compensation expense	395	208	812	446
Income tax benefit	150	79	309	169
Total stock-based compensation expense, net of tax	245	129	503	277
Cost of Sales [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense		6		32
Operating Expense [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	395	200	812	403
Research and Development Expense [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense		$ 2		$ 11