Stock Option Plans - Summary of Option Activity (Details)	3 Months Ended
	Mar. 31, 2017 USD ($) $ / shares shares
Number of Shares
Outstanding at beginning of period (in shares) | shares	833,630
Granted (in shares) | shares	0
Exercised (in shares) | shares	(16,250)
Expired/Forfeited (in shares) | shares	0
Outstanding at end of period (in shares) | shares	817,380
Exercisable at end of period (in shares) | shares	359,005
Weighted Average Exercise Price per share
Outstanding at beginning of period (in usd per share) | $ / shares	$ 49.92
Granted (in usd per share) | $ / shares	0.00
Exercised (in usd per share) | $ / shares	49.52
Expired/Forfeited (in usd per share) | $ / shares	0.00
Outstanding at end of period (in usd per share) | $ / shares	49.93
Exercisable at end of period (in usd per share) | $ / shares	$ 46.55
Aggregate Intrinsic Value
Outstanding at beginning of period | $	$ 13,913,891
Granted | $	0
Exercised | $	238,704
Expired/Forfeited | $
Outstanding at end of period | $	9,557,370
Exercisable at end of period | $	$ 5,411,144