Quarterly report pursuant to Section 13 or 15(d)

Dividends (Detail)

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Dividends (Detail) (USD $)
3 Months Ended 6 Months Ended 1 Months Ended
Jun. 30, 2012
Jun. 30, 2011
Jun. 30, 2012
Jun. 30, 2011
Jul. 30, 2012
Subsequent Event
Stockholders Equity [Line Items]          
Paid cash dividends, per share     $ 0.08 $ 0.04  
Dividends payable, date declared, day, month and year     Jul. 30, 2012    
Dividend declared per common share $ 0.08 $ 0.04 $ 0.16 $ 0.08 $ 0.08
Dividends payable, date to be paid, day, month and year     Sep. 12, 2012    
Dividends payable, date of record, day, month and year     Aug. 22, 2012