Share-Based Compensation (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	May 31, 2012	May 31, 2011	May 31, 2012	May 31, 2011
Share-based compensation expense [Line Items]
Share-based compensation	$ 18,946	$ 19,963	$ 59,438	$ 50,453
Stock options granted	3		12
Weighted average grant date fair value of options	$ 14.20		$ 16.64
Quarter To Date [Member]
Share-based compensation expense [Line Items]
Weighted average exercise price of options granted	$ 42.41		$ 42.41
Year To Date [Member]
Share-based compensation expense [Line Items]
Weighted average exercise price of options granted	$ 45.74		$ 45.74
Instructional and student advisory [Member]
Share-based compensation expense [Line Items]
Share-based compensation	6,518	7,598	20,641	19,319
Marketing [Member]
Share-based compensation expense [Line Items]
Share-based compensation	1,533	1,347	5,473	4,056
Admissions advisory [Member]
Share-based compensation expense [Line Items]
Share-based compensation	405	585	1,277	1,742
General and administrative [Member]
Share-based compensation expense [Line Items]
Share-based compensation	$ 10,490	$ 10,433	$ 32,047	$ 25,336