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Components Of Equity And Comprehensive Income - Additional Information (Detail) (USD $)
6 Months Ended
Jun. 30, 2011
Jun. 30, 2010
Class of Stock [Line Items]    
Date of declaration of dividends May 04, 2011 May 05, 2010
Dividend declared per share $ 0.25 $ 0.20
Dividend Payable Date Declared Day Month Year Jun. 15, 2011 Jun. 15, 2010
Dividends payable to shareholders date of record Jun. 01, 2011 Jun. 01, 2010