Incentive Plan (Summary Of Stock Options Outstanding And Exercisable) (Details) (USD $)	9 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Number outstanding	123,690	129,259
Weighted average remaining contractual life (years), Outstanding	2 years 7 months 28 days
Weighted average exercise price, Outstanding	$ 30.13
Aggregate intrinsic value, Outstanding	$ 2,841,388
$12.00-13.02 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price, lower limit	$ 12.00
Exercise price, upper limit	$ 13.02
Number outstanding	34,870
Weighted average remaining contractual life (years), Outstanding	1 year 29 days
Weighted average exercise price, Outstanding	$ 12.00
Aggregate intrinsic value, Outstanding	1,433,157
$20.37-28.09 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price, lower limit	$ 20.37
Exercise price, upper limit	$ 28.09
Number outstanding	17,000
Weighted average remaining contractual life (years), Outstanding	2 years 1 month 21 days
Weighted average exercise price, Outstanding	$ 21.28
Aggregate intrinsic value, Outstanding	540,970
$33.18-41.73 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price, lower limit	$ 33.18
Exercise price, upper limit	$ 41.73
Number outstanding	71,820
Weighted average remaining contractual life (years), Outstanding	3 years 6 months 18 days
Weighted average exercise price, Outstanding	$ 41.02
Aggregate intrinsic value, Outstanding	$ 867,261