Computations of Basic and Diluted Earnings Per Share (Parenthetical) (Detail) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2013	Mar. 31, 2012
Earnings Per Share Disclosure [Line Items]
Shares of unvested restricted stock	1,128	1,200

This element represents nonvested share-based payment awards that contain non-forfeitable rights to dividends or dividend equivalents (whether paid or unpaid). Basic and dilutive earnings per share are generally disclosed for such shares using the two-class method.

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+ Details