Share-Based Compensation - Option Price Ranges (Details) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Options Outstanding, Number Outstanding (in shares)	217,875
Options Outstanding, Weighted-Average Remaining Contractual Life (Years)	2 years 6 months 25 days	2 years 7 months 6 days	3 years 18 days	2 years 11 months 8 days
Options Outstanding, Weighted-Average Exercise Price (in dollars per share)	$ 45.97
Options Exercisable, Number of Shares	115,125
Options Exercisable, Weighted-Average Exercise Price (in dollars per share)	$ 49.17
$35.70 Exercise Price Range
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Shares authorized under stock option plans, exercise price range, lower range limit	35.70
Shares authorized under stock option plans, exercise price range, upper range limit	$ 35.70
Options Outstanding, Number Outstanding (in shares)	36,000
Options Outstanding, Weighted-Average Remaining Contractual Life (Years)	9 months 25 days
Options Outstanding, Weighted-Average Exercise Price (in dollars per share)	$ 5.90
Options Exercisable, Number of Shares	0
Options Exercisable, Weighted-Average Exercise Price (in dollars per share)	$ 0
$41.60 Exercise Price Range
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Shares authorized under stock option plans, exercise price range, lower range limit	41.60
Shares authorized under stock option plans, exercise price range, upper range limit	$ 41.60
Options Outstanding, Number Outstanding (in shares)	36,000
Options Outstanding, Weighted-Average Remaining Contractual Life (Years)	5 months 12 days
Options Outstanding, Weighted-Average Exercise Price (in dollars per share)	$ 6.87
Options Exercisable, Number of Shares	11,250
Options Exercisable, Weighted-Average Exercise Price (in dollars per share)	$ 4.07
$42.56 Exercise Price Range
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Shares authorized under stock option plans, exercise price range, lower range limit	42.56
Shares authorized under stock option plans, exercise price range, upper range limit	$ 42.56
Options Outstanding, Number Outstanding (in shares)	36,000
Options Outstanding, Weighted-Average Remaining Contractual Life (Years)	6 months
Options Outstanding, Weighted-Average Exercise Price (in dollars per share)	$ 7.03
Options Exercisable, Number of Shares	18,000
Options Exercisable, Weighted-Average Exercise Price (in dollars per share)	$ 6.65
$49.22 Exercise Price Range
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Shares authorized under stock option plans, exercise price range, lower range limit	49.22
Shares authorized under stock option plans, exercise price range, upper range limit	$ 49.22
Options Outstanding, Number Outstanding (in shares)	40,875
Options Outstanding, Weighted-Average Remaining Contractual Life (Years)	21 days
Options Outstanding, Weighted-Average Exercise Price (in dollars per share)	$ 9.23
Options Exercisable, Number of Shares	40,875
Options Exercisable, Weighted-Average Exercise Price (in dollars per share)	$ 17.48
$52.92 Exercise Price Range
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Shares authorized under stock option plans, exercise price range, lower range limit	52.92
Shares authorized under stock option plans, exercise price range, upper range limit	$ 52.92
Options Outstanding, Number Outstanding (in shares)	30,000
Options Outstanding, Weighted-Average Remaining Contractual Life (Years)	5 months 19 days
Options Outstanding, Weighted-Average Exercise Price (in dollars per share)	$ 7.29
Options Exercisable, Number of Shares	11,250
Options Exercisable, Weighted-Average Exercise Price (in dollars per share)	$ 5.17
$53.90 Exercise Price Range
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Shares authorized under stock option plans, exercise price range, lower range limit	53.90
Shares authorized under stock option plans, exercise price range, upper range limit	$ 53.90
Options Outstanding, Number Outstanding (in shares)	39,000
Options Outstanding, Weighted-Average Remaining Contractual Life (Years)	3 months 7 days
Options Outstanding, Weighted-Average Exercise Price (in dollars per share)	$ 9.65
Options Exercisable, Number of Shares	33,750
Options Exercisable, Weighted-Average Exercise Price (in dollars per share)	$ 15.80