Annual report pursuant to Section 13 and 15(d)

Stock Option and Purchase Plans - Summary of Company's Stock Option Activity and Related Information (Detail)

v3.3.1.900
Stock Option and Purchase Plans - Summary of Company's Stock Option Activity and Related Information (Detail) - USD ($)
$ / shares in Units, $ in Thousands
 12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Options      
Balance at beginning of the period (in shares) 1,466,238 1,945,497 2,099,364
Options granted (in shares) 91,950 84,905 96,214
Options exercised (in shares) (301,710) (560,051) (250,081)
Options forfeited (in shares) 0 (4,113) 0
Balance at end of the period (in shares) 1,256,478 1,466,238 1,945,497
Exercisable at end of the period (in shares) 1,014,817 1,192,708 1,586,354
Weighted Average Exercise Price      
Balance at beginning of the period (in usd per share) $ 10.85 $ 7.57 $ 5.97
Options granted (in usd per share) 41.17 42.13 30.92
Options exercised (in usd per share) 4.89 4.17 3.08
Options forfeited (in usd per share) 0.00 13.16 0.00
Balance at end of the period (in usd per share) 14.50 10.85 7.57
Exercisable at end of the period (in usd per share) $ 10.58 $ 7.57 $ 5.66
Aggregate Intrinsic Value      
Balance at beginning of the period (in usd) $ 43,778 $ 78,846 $ 65,072
Options granted (in usd) (42) 506 581
Options exercised (in usd) (10,808) (24,599) (8,472)
Options forfeited (in usd) 0 (144) 0
Balance at end of the period (in usd) 32,928 54,609 57,181
Exercisable at end of the period (in usd) $ 30,576 $ 48,331 $ 49,648