Quarterly report pursuant to Section 13 or 15(d)

Basic and Diluted Net Earnings Per Share - Additional Information (Detail)

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Basic and Diluted Net Earnings Per Share - Additional Information (Detail)
3 Months Ended 6 Months Ended
Jun. 30, 2012
Jun. 30, 2011
Jun. 30, 2012
Jun. 30, 2011
Earnings Per Share Disclosure [Line Items]        
Dilutive shares 24,356,298 24,491,530 24,460,623 24,625,391
Common Class A
       
Earnings Per Share Disclosure [Line Items]        
Outstanding options to purchase shares     2,106,674 1,114,675
Dilutive shares     213,476 212,279