Stock-based Employee Compensation, Stock Option Plans, and Deferred Compensation Plan for Directors - Summary of Option Activity (Details)	9 Months Ended
	Sep. 30, 2020 USD ($) $ / shares shares
Number of Shares
Outstanding at beginning of period (in shares) | shares	1,309,614
Granted (in shares) | shares	238,000
Exercised (in shares) | shares	(10,749)
Expired/Forfeited (in shares) | shares	(21,250)
Outstanding at end of period (in shares) | shares	1,515,615
Exercisable at end of period (in shares) | shares	978,240
Weighted Average Exercise Price per share
Outstanding at beginning of period (in usd per share) | $ / shares	$ 53.38
Granted (in usd per share) | $ / shares	50.00
Exercised (in usd per share) | $ / shares	49.19
Expired/Forfeited (in usd per share) | $ / shares	53.96
Outstanding at end of period (in usd per share) | $ / shares	52.87
Exercisable at end of period (in usd per share) | $ / shares	$ 53.03
Aggregate Intrinsic Value
Outstanding at beginning of period | $	$ 2,528,463
Granted | $	0
Exercised | $	85,268
Expired/Forfeited | $	0
Outstanding at end of period | $	0
Exercisable at end of period | $	$ 0