Stock Options (Schedule of Qualified Stock Option Activity) (Details) - Qualified Stock Options - $ / shares		12 Months Ended
		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		301,800	292,350	330,730
Granted		29,500	48,250	49,000
Exercised		(75,355)	(27,700)	(81,880)
Canceled		(1,750)	(11,100)	(5,500)
Options outstanding at end of year		254,195	301,800	292,350
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]	$ 30.73	$ 26.68	$ 21.82
Granted, Exercise Price, in dollars per share	[1]	53.95	52.67	42.70
Exercised, Exercise Price, in dollars per share	[1]	26.11	24.33	16.77
Cancelled, Exercise Price, in dollars per share	[1]	53.61	35.42	24.24
Outstanding at end of year, Exercise Price, in dollars per share	[1]	$ 34.64	$ 30.73	$ 26.68
Options exercisable at end of year		143,345	172,450	154,950
Exercisable at end of year, Exercise Price, in dollars per share	[1]	$ 25.69	$ 22.30	$ 21.57
Options available for grant at end of year		370,750	28,950	66,100

[1] Weighted Averages