Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurement (Narrative) (Details)

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Fair Value Measurement (Narrative) (Details) (USD $)
Feb. 29, 2012
Aug. 31, 2011
Feb. 28, 2011
Mar. 27, 2012
2% Convertible Notes [Member]
Feb. 29, 2012
2% Convertible Notes [Member]
Aug. 31, 2011
2% Convertible Notes [Member]
Nov. 30, 2003
2% Convertible Notes [Member]
Feb. 29, 2012
Senior Notes [Member]
Aug. 31, 2011
Senior Notes [Member]
Fair Value Measurement [Line Items]                  
Outstanding debt, amount $ 158,000,000 $ 158,000,000     $ 117,600,000     $ 250,000,000  
Fair value of long-term debt         $ 170,500,000 $ 127,900,000   $ 259,400,000 $ 252,500,000
Interest rate on Convertible Notes 2.00%   2.00% 2.00% 2.00%   2.00%