Stock Options (Schedule of Qualified Stock Options Outstanding and Exercisable) (Details) - Qualified Stock Options - $ / shares		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding (in shares)		220,820	254,195	301,800	292,350
Options Exercisable (in shares)		136,220	143,345	172,450
$11.45 - $22.55
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, Lower Range Limit (in dollars per share)		$ 11.45
Range of Exercise Price, Upper Range Limit (in dollars per share)		$ 22.55
Options Outstanding, Exercise price range (in shares)		44,320
Options Outstanding, Remaining Contractual Life	[1]	2 years 11 days
Options, Outstanding, Exercise Price (in dollars per share)	[1]	$ 15.08
Options Exercisable, Exercise price range (in shares)		44,320
Options Exercisable, Exercise Price (in dollars per share)	[1]	$ 15.08
$24.69 - $42.70
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, Lower Range Limit (in dollars per share)		24.69
Range of Exercise Price, Upper Range Limit (in dollars per share)		$ 42.70
Options Outstanding, Exercise price range (in shares)		96,350
Options Outstanding, Remaining Contractual Life	[1]	5 years 3 months 18 days
Options, Outstanding, Exercise Price (in dollars per share)	[1]	$ 34.07
Options Exercisable, Exercise price range (in shares)		73,750
Options Exercisable, Exercise Price (in dollars per share)	[1]	$ 32.64
$49.44 - $54.87
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, Lower Range Limit (in dollars per share)		49.44
Range of Exercise Price, Upper Range Limit (in dollars per share)		$ 54.87
Options Outstanding, Exercise price range (in shares)		80,150
Options Outstanding, Remaining Contractual Life	[1]	8 years 2 months 16 days
Options, Outstanding, Exercise Price (in dollars per share)	[1]	$ 53.72
Options Exercisable, Exercise price range (in shares)		18,150
Options Exercisable, Exercise Price (in dollars per share)	[1]	$ 53.17

[1] Weighted Averages