Annual report pursuant to Section 13 and 15(d)

Fair Value Measurements - Additional Information (Detail)

v2.4.0.6
Fair Value Measurements - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified
Aug. 31, 2012
5.625% Senior Notes
Apr. 16, 2012
5.625% Senior Notes
Aug. 31, 2012
6.875% Senior Notes
Apr. 16, 2012
6.875% Senior Notes
Aug. 31, 2011
6.875% Senior Notes
Aug. 31, 2012
2% Convertible Notes
Aug. 31, 2011
2% Convertible Notes
Aug. 31, 2010
2% Convertible Notes
Nov. 30, 2003
2% Convertible Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]                  
Outstanding debt, amount $ 300.0       $ 250.0   $ 117.8    
Debt instrument, interest rate 5.625% 5.625% 6.875% 6.875% 6.875% 2.00% 2.00% 2.00% 2.00%
Fair value of long-term debt $ 309.8       $ 252.5   $ 127.9