Share-based Compensation - Option Price Ranges (Details) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Stock options outstanding (in shares)	217,875
Stock options outstanding, weighted average remaining contractual term (in years)	2 years 7 months 6 days	3 years 18 days	2 years 11 months 8 days	3 years 3 months 10 days
Stock options outstanding, weighted average exercise price (in dollars per share)	$ 43.78	$ 42.75	$ 37.68	$ 30.73
Stock options exercisable (in shares)	109,125
Stock options, exercisable, weighted average exercise price (in dollars per share)	$ 40.92
$21.19 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	21.19
Shares authorized under stock option plans, exercise price range, upper range limit	$ 21.19
Stock options outstanding, by exercise price range	30,000
Stock options outstanding, weighted average remaining contractual term (in years)	0 days
Stock options outstanding, weighted average exercise price, by exercise price range (in dollars per share)	$ 2.92
Stock options exercisable, by exercise price range	30,000
Stock options exercisable, weighted average exercise price, by exercise price range (in dollars per share)	$ 5.83
$28.59 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	28.59
Shares authorized under stock option plans, exercise price range, upper range limit	$ 28.59
Stock options outstanding, by exercise price range	6,000
Stock options outstanding, weighted average remaining contractual term (in years)	0 months
Stock options outstanding, weighted average exercise price, by exercise price range (in dollars per share)	$ 0.79
Stock options exercisable, by exercise price range	6,000
Stock options exercisable, weighted average exercise price, by exercise price range (in dollars per share)	$ 1.57
$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	41.6
Shares authorized under stock option plans, exercise price range, upper range limit	$ 41.6
Stock options outstanding, by exercise price range	36,000
Stock options outstanding, weighted average remaining contractual term (in years)	18 days
Stock options outstanding, weighted average exercise price, by exercise price range (in dollars per share)	$ 6.87
Stock options exercisable, by exercise price range	0
Stock options exercisable, weighted average exercise price, by exercise price range (in dollars per share)	$ 0
$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
Stock options outstanding, by exercise price range	36,000
Stock options outstanding, weighted average remaining contractual term (in years)	7 months 28 days
Stock options outstanding, weighted average exercise price, by exercise price range (in dollars per share)	$ 7.03
Stock options exercisable, by exercise price range	9,000
Stock options exercisable, weighted average exercise price, by exercise price range (in dollars per share)	$ 3.50
$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
Stock options outstanding, by exercise price range	40,875
Stock options outstanding, weighted average remaining contractual term (in years)	3 months
Stock options outstanding, weighted average exercise price, by exercise price range (in dollars per share)	$ 9.23
Stock options exercisable, by exercise price range	38,625
Stock options exercisable, weighted average exercise price, by exercise price range (in dollars per share)	$ 17.42
$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
Stock options outstanding, by exercise price range	30,000
Stock options outstanding, weighted average remaining contractual term (in years)	7 months 9 days
Stock options outstanding, weighted average exercise price, by exercise price range (in dollars per share)	$ 7.29
Stock options exercisable, by exercise price range	0
Stock options exercisable, weighted average exercise price, by exercise price range (in dollars per share)	$ 0
$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
Stock options outstanding, by exercise price range	39,000
Stock options outstanding, weighted average remaining contractual term (in years)	5 months 12 days
Stock options outstanding, weighted average exercise price, by exercise price range (in dollars per share)	$ 9.65
Stock options exercisable, by exercise price range	25,500
Stock options exercisable, weighted average exercise price, by exercise price range (in dollars per share)	$ 12.60