XML 51 R41.htm IDEA: XBRL DOCUMENT v3.8.0.1
Stock Option Plans - Summary of Option Activity (Details)
 3 Months Ended
Mar. 31, 2018
USD ($)
$ / shares
shares
Number of Shares  
Outstanding at beginning of period (in shares) | shares 913,320
Granted (in shares) | shares 0
Exercised (in shares) | shares (7,650)
Expired/Forfeited (in shares) | shares 0
Outstanding at end of period (in shares) | shares 905,670
Exercisable at end of period (in shares) | shares 423,295
Weighted Average Exercise Price per share  
Outstanding at beginning of period (in usd per share) | $ / shares $ 52.80
Granted (in usd per share) | $ / shares 0.00
Exercised (in usd per share) | $ / shares 41.82
Expired/Forfeited (in usd per share) | $ / shares 0.00
Outstanding at end of period (in usd per share) | $ / shares 52.89
Exercisable at end of period (in usd per share) | $ / shares $ 49.06
Aggregate Intrinsic Value  
Outstanding at beginning of period | $ $ 8,172,970
Granted | $ 0
Exercised | $ 153,306
Expired/Forfeited | $
Outstanding at end of period | $ 1,683,170
Exercisable at end of period | $ $ 1,520,644