Per Share Data (Details) - $ / shares	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Aug. 27, 2015
Earnings Per Share [Abstract]
Convertible securities which would affect denominator in calculating basic and dilutive earnings per share (in shares)	0
Options, outstanding (in shares)	96,500	32,500	26,500	34,750	26,500
Outstanding, weighted average exercise price (in dollars per share)	$ 43.61	$ 42.03	$ 42.03	$ 42.03
Weighted average exercise price (in dollars per share)		42.03
Share price (in dollars per share)	$ 46.94	$ 39.02
Weighted average common shares outstanding - basic (in shares)	4,734,805	4,740,503
Dilutive effect of outstanding stock options (in shares)	26,500	0
Weighted average common shares outstanding - diluted (in shares)	4,761,305	4,740,503