Annual report pursuant to Section 13 and 15(d)

Equity Compensation - Summary of Company's Stock Option Activity and Related Information (Details)

v3.10.0.1
Equity Compensation - Summary of Company's Stock Option Activity and Related Information (Details) - Stock Option - USD ($)
$ / shares in Units, $ in Thousands
 12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Options      
Balance at beginning of the period (in shares) 1,506,604 1,539,017 1,661,700
Options granted (in shares) 120,270 118,612 120,635
Options exercised (in shares) (274,941) (131,904) (217,083)
Options forfeited (in shares) (24,014) (19,121) (26,235)
Balance at end of the period (in shares) 1,327,919 1,506,604 1,539,017
Exercisable at end of the period (in shares) 1,043,596 1,252,315 1,255,295
Weighted Average Exercise Price      
Balance at beginning of the period (in usd per share) $ 14.65 $ 12.91 $ 10.96
Options granted (in usd per share) 32.33 33.40 29.82
Options exercised (in usd per share) 3.89 9.77 6.26
Options forfeited (in usd per share) 34.13 24.27 22.57
Balance at end of the period (in usd per share) 18.13 14.65 12.91
Exercisable at end of the period (in usd per share) $ 14.27 $ 11.17 $ 9.59
Aggregate Intrinsic Value      
Balance at beginning of the period (in usd) $ 23,801 $ 35,630 $ 30,675
Options granted (in usd) (226) 315 (48)
Options exercised (in usd) (7,303) (3,467) (5,029)
Options forfeited (in usd) 88 (225) (180)
Balance at end of the period (in usd) 16,360 32,253 25,418
Exercisable at end of the period (in usd) $ 16,885 $ 31,177 $ 24,898