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Summary of Stock Option (Detail)
 3 Months Ended
Mar. 31, 2016
USD ($)
$ / shares
shares
Options  
Beginning balance | shares 2,242,202
Exercises | shares (30,375)
Cancellations | shares (23,375)
Expirations | shares (800)
Ending balance | shares 2,187,652
Options exercisable at End of Period | shares 1,694,819
Weighted-average exercise price  
Beginning balance | $ / shares $ 14.28
Exercises | $ / shares 3.78
Cancellations | $ / shares 15.32
Expirations | $ / shares 15.95
Ending balance | $ / shares 14.41
Options exercisable at End of Period | $ / shares $ 14.03
Weighted-average remaining contractual life (years)  
Options outstanding, Ending balance 4 years 9 months 18 days
Options exercisable, Ending balance 4 years 1 month 6 days
Aggregate intrinsic value  
Options outstanding, end of period | $ $ 6,171,200
Options exercisable, end of period | $ $ 5,584,600