Earnings Per Share - Additional Information (Detail)
3 Months Ended 9 Months Ended
Sep. 30, 2012
Sep. 30, 2011
Sep. 30, 2012
Sep. 30, 2011
Dec. 31, 2011
Earnings Per Share [Line Items]          
Average number of shares outstanding 11,056,999 11,432,209 11,111,490 11,453,124  
Number of shares outstanding 11,057,052   11,057,052   11,309,365