Share-Based Compensation (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Nov. 30, 2011	Nov. 30, 2010
Share-based compensation expense [Line Items]
Share-based compensation	$ 20,892	$ 15,032
Stock options granted	4
Weighted average grant date fair value of options	$ 15.85
Weighted average exercise price of options granted	$ 42.60
Instructional and student advisory [Member]
Share-based compensation expense [Line Items]
Share-based compensation	7,422	5,481
Marketing [Member]
Share-based compensation expense [Line Items]
Share-based compensation	2,234	1,386
Admissions advisory [Member]
Share-based compensation expense [Line Items]
Share-based compensation	447	556
General and administrative [Member]
Share-based compensation expense [Line Items]
Share-based compensation	$ 10,789	$ 7,609