Note 6 - Investment in Westinghouse and Related Agreements (Detail)
0 Months Ended 48 Months Ended
Oct. 16, 2006
USD ($)
Oct. 16, 2010
USD ($)
Nov. 30, 2012
USD ($)
Aug. 31, 2012
USD ($)
Oct. 16, 2006
JPY (¥)
Oct. 13, 2006
USD ($)
Oct. 13, 2006
JPY (¥)
Nov. 30, 2012
Toshiba Nuclear Energy Holdings Inc [Member]
USD ($)
Nov. 30, 2012
Toshiba Nuclear Energy Holdings Inc [Member]
JPY (¥)
Oct. 16, 2006
Toshiba Nuclear Energy Holdings Inc [Member]
Nov. 30, 2012
Interest [Member]
USD ($)
Nov. 30, 2012
Principal [Member]
USD ($)
Equity Method Investment, Ownership Percentage                   20.00%    
Business Acquisition, Cost of Acquired Entity, Purchase Price $ 1,100,000,000         $ 1,100,000,000            
Debt Instrument, Face Amount 1,080,000,000       128,980,000,000 1,100,000,000 128,980,000,000 1,519,100,000 124,700,000,000      
Proceeds from Issuance of Debt 1,000,000,000 1,000,000,000                    
Letters of Credit Outstanding, Amount     $ 314,600,000 $ 329,600,000             $ 18,200,000 $ 52,400,000