Note 6 - Investment in Westinghouse and Related Agreements (Detail)
0 Months Ended 3 Months Ended
Oct. 16, 2006
USD ($)
Nov. 30, 2011
USD ($)
Aug. 31, 2011
USD ($)
Oct. 31, 2007
JPY (¥)
Oct. 13, 2006
USD ($)
Oct. 13, 2006
JPY (¥)
Oct. 16, 2006
Toshiba Nuclear Energy Holdings Inc [Member]
Nov. 30, 2011
Principal [Member]
USD ($)
Nov. 30, 2011
Interest [Member]
USD ($)
Equity Method Investment, Ownership Percentage   20.00%         20.00%    
Business Acquisition, Cost of Acquired Entity, Purchase Price $ 1,100,000,000       $ 1,100,000,000        
Debt Instrument, Face Amount (in Yen)       128,980,000,000 1,100,000,000 128,980,000,000      
Proceeds from Issuance of Debt 1,000,000,000 1,000,000,000              
Letters of Credit Outstanding, Amount   $ 431,800,000 $ 456,100,000         $ 55,100,000 $ 57,700,000