Stock Options (Schedule of Non-Qualified Stock Options Activity) (Details) - Non Qualified Options - $ / shares		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options outstanding at beginning of year (in shares)		127,300	132,100	114,700
Granted (in shares)		0	0	29,000
Exercised (in shares)		(14,900)	(4,800)	(11,600)
Canceled (in shares)		0	0	0
Options outstanding at end of year (in shares)		112,400	127,300	132,100
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]	$ 32.05	$ 31.30	$ 24.87
Granted, Exercise Price (in dollars per share)	[1]	0.00	0.00	53.51
Exercised, Exercise Price (in dollars per share)	[1]	13.73	11.45	23.29
Canceled, 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]	$ 32.05	$ 31.30	$ 24.87	$ 34.48	$ 32.05	$ 31.30
Options exercisable at end of year (in shares)					85,000	83,100	71,100
Exercisable at end of year, Exercise Price (in dollars per share)	[1]				$ 29.61	$ 24.54	$ 19.85
Options available for grant at end of year (in shares)					207,608	232,522	258,526

[1] Weighted Averages