Quarterly report pursuant to Section 13 or 15(d)

Summary Of Stock Option Activity (Detail)

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Summary Of Stock Option Activity (Detail) (USD $)
In Thousands, except Share data, unless otherwise specified
 6 Months Ended
Jun. 30, 2012
Jun. 30, 2011
Shares    
Beginning balance 1,073,800 881,000
Granted 36,500 166,500
Exercised (52,136) (5,000)
Ending balance 1,058,164 1,042,500
Exercisable end of period 434,706 332,459
Weighted Average Exercise Price    
Beginning balance $ 18.33 $ 15.65
Granted $ 30.00 $ 26.05
Exercised $ 11.00 $ 10.50
Ending balance $ 19.11 $ 17.34
Exercisable at end of period $ 13.31 $ 12.71
Weighted Average Remaining Contractual Term (years)    
Beginning balance 6 years 6 years 10 months 24 days
Granted 9 years 8 months 12 days 9 years 7 months 6 days
Exercised 3 years 7 months 6 days 4 years 4 months 24 days
Ending balance 5 years 9 months 18 days 6 years 2 months 12 days
Exercisable at end of period 3 years 10 months 24 days 4 years 9 months 18 days
Aggregate Intrinsic Value    
Beginning balance $ 12,508 $ 8,238
Granted      
Exercised 991 98
Ending balance 11,527 13,203
Exercisable at end of period $ 7,257 $ 5,748