Stock Options (Schedule of Qualified Stock Options Outstanding and Exercisable) (Details) - Qualified Stock Options - $ / shares		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding, Shares, Total		254,195	301,800	292,350	330,730
Options Exercisable, Shares, Total		143,345	172,450	154,950
$11.45 - $22.39
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, Lower Range Limit		$ 11.45
Range of Exercise Price, Upper Range Limit		$ 22.39
Options Outstanding, Shares		43,225
Options Outstanding, Remaining Contractual Life	[1]	2 years 11 months 27 days
Options, Outstanding, Exercise Price	[1]	$ 12.72
Options Exercisable, Shares		43,225
Options Exercisable, Exercise Price	[1]	$ 12.72
$22.55 - $42.70
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, Lower Range Limit		22.55
Range of Exercise Price, Upper Range Limit		$ 42.70
Options Outstanding, Shares		138,970
Options Outstanding, Remaining Contractual Life	[1]	5 years 4 months 24 days
Options, Outstanding, Exercise Price	[1]	$ 31.88
Options Exercisable, Shares		91,570
Options Exercisable, Exercise Price	[1]	$ 29.30
$49.44 - $54.24
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, Lower Range Limit		49.44
Range of Exercise Price, Upper Range Limit		$ 54.24
Options Outstanding, Shares		72,000
Options Outstanding, Remaining Contractual Life	[1]	8 years 9 months 29 days
Options, Outstanding, Exercise Price	[1]	$ 53.12
Options Exercisable, Shares		8,550
Options Exercisable, Exercise Price	[1]	$ 52.56

[1] Weighted Averages