Equity Compensation and Related Plans - Summary of stock options (Details)	12 Months Ended
	Dec. 31, 2018 $ / shares shares
Exercise Price Range $15.00 to 20.00
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding, Shares | shares	13,300
Options Outstanding, Range Minimum	$ 15.00
Options Outstanding, Range Maximum	20.00
Options Outstanding, Weighted Average Price	$ 16.35
Options Outstanding, Average Remaining Life	5 years 4 months 28 days
Options Exercisable, Shares | shares	13,300
Options Exercisable, Weighted Average Price	$ 16.35
Exercise Price Range $20.01 to 25.00
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding, Shares | shares	500
Options Outstanding, Range Minimum	$ 20.01
Options Outstanding, Range Maximum	25.00
Options Outstanding, Weighted Average Price	$ 22.95
Options Outstanding, Average Remaining Life	1 year 2 months 19 days
Options Exercisable, Shares | shares	500
Options Exercisable, Weighted Average Price	$ 22.95
Exercise Price Range $25.01 to 30.00
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding, Shares | shares	1,023
Options Outstanding, Range Minimum	$ 25.01
Options Outstanding, Range Maximum	30.00
Options Outstanding, Weighted Average Price	$ 29.45
Options Outstanding, Average Remaining Life	26 days
Options Exercisable, Shares | shares	1,023
Options Exercisable, Weighted Average Price	$ 29.45
Exercise Price Range $30.01 to 31.50
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding, Shares | shares	32,316
Options Outstanding, Range Minimum	$ 30.01
Options Outstanding, Range Maximum	31.50
Options Outstanding, Weighted Average Price	$ 31.47
Options Outstanding, Average Remaining Life	6 months
Options Exercisable, Shares | shares	32,316
Options Exercisable, Weighted Average Price	$ 31.47
Exercise Price Range $15.00 to 31.50
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding, Shares | shares	47,139
Options Outstanding, Range Minimum	$ 15.00
Options Outstanding, Range Maximum	31.50
Options Outstanding, Weighted Average Price	$ 27.07
Options Outstanding, Average Remaining Life	1 year 8 months 78 days
Options Exercisable, Shares | shares	47,139
Options Exercisable, Weighted Average Price	$ 27.07