Stock Options (Schedule of Non-Qualified Stock Options Activity) (Details) - Non Qualified Options - $ / shares		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options outstanding at beginning of year		132,100	114,700	89,700
Granted		0	29,000	25,000
Exercised		(4,800)	(11,600)	0
Canceled		0	0	0
Options outstanding at end of year		127,300	132,100	114,700
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Outstanding at beginning of year, Exercise Price, in dollars per share	[1]	$ 31.30	$ 24.87	$ 19.91
Granted, Exercise Price, in dollars per share	[1]	0.00	53.51	42.70
Exercised, Exercise Price, in dollars per share	[1]	11.45	23.29	0.00
Cancelled, Exercise Price, in dollars per share	[1]	0.00	0.00	0.00
Outstanding at end of year, Exercise Price, in dollars per share	[1]	$ 31.30	$ 24.87	$ 19.91	$ 32.05	$ 31.30	$ 24.87
Options exercisable at end of year		83,100	71,100	57,900
Exercisable at end of year, Exercise Price, in dollars per share	[1]				$ 24.54	$ 19.85	$ 19.89
Options available for grant at end of year					232,522	258,526	293,526

[1] Weighted Averages